Why 47% of campaigns fail before sending

You send a campaign. It’s well-written, segmented, timed perfectly. Then you check the reports and see: 47% of your emails never reached an inbox. Not because of poor copy, but because the addresses were invalid, quarantined, or outright toxic.

Deliverability doesn’t start when the send button is pressed. It begins weeks before—during list building, domain setup, and infrastructure alignment. A single invalid address in a bulk send can trip spam filters. Especially at scale, even one bad address can expose your sender reputation to risk.

Most ESPs rely on basic syntax checks and assume all addresses are deliverable. That’s a flaw. Without technical validation, even flawless content fails. Your message never lands because the underlying infrastructure was never validated. That’s why pre-campaign deliverability validation is not optional—it’s foundational.

Key takeaways

  • Deliverability issues often originate before the first email is sent, during list or infrastructure prep.
  • Invalid or risky addresses in bulk sends can trigger spam filters and degrade sender reputation.
  • Pre-campaign verification of addresses, domains, and alignment with email infrastructure prevents premature campaign failure.

What is pre-campaign deliverability validation for ESPs?

You’re validating your email list and sender setup before sending to ensure messages reach inboxes, not spam folders or hard bounces. It checks for invalid, disposable, role, and catch-all addresses—and confirms your DNS settings (SPF, DKIM, DMARC) are correct while assessing domain reputation. Real inbox placement tests simulate delivery across major providers to predict campaign performance. The goal? Lower bounce rates, higher trust, and better inbox placement—before you send.

How it works in practice

Let’s walk through what happens behind the scenes. First, you upload your list. Tools like MailTester scan each address to spot dead, role-based, or disposable email patterns that hurt sender reputation. A single address like [email protected] or [email protected] may not be a hard bounce, but it’s still a risk. If 5% of your list falls into this category, your sender reputation takes a hit—especially if repeated.

Next, DNS records are validated. SPF, DKIM, and DMARC aren’t just technical checkboxes—they’re trust signals. A misconfigured SPF can trigger rejection. DMARC reports, while often ignored, help you see how your domain is being used. If a domain has poor authentication, even legitimate mail may not pass gatekeeping. You can verify these in real time with tools like the MailTester email checker.

Testing inbox placement before sending

Just because an address is valid doesn’t mean it lands in the inbox. That’s where inbox placement testing comes in. Instead of guessing, you simulate sends to real user accounts across Gmail, Outlook, and Apple Mail. These tests measure delivery rates, spam filter scores, and actual inbox placement. Tools like the MailTester inbox tester use real email providers—so you see the conditions your campaign will face.

In the real world, domain reputation is a moving target. The same domain might be trusted today but blacklisted tomorrow due to spam reports. Regular validation prevents surprise drops in deliverability. It’s not a one-time fix. It’s an ongoing practice that integrates into your marketing workflow—even before you send a single campaign.

For teams using SendGrid, Mailchimp, or HubSpot, MailTester integrates directly, letting you verify before you sync. The result? Fewer wasted sends, cleaner data, and better sender trust. And unlike some tools that promise 99% accuracy, MailTester’s real-time checks are grounded in actual SMTP behavior—no guesswork.

Primary keywords: pre-campaign deliverability validation checklist for email service providers

You need a pre-campaign deliverability validation checklist to stop guessing whether your emails will land in inboxes. Without it, you risk blocklisting, high bounce rates, and damaged sender reputation — all of which hurt deliverability at scale. This checklist works regardless of your email service provider or sender domain, and every step directly impacts inbox placement.

Why this checklist is non-negotiable for large-scale senders

Every big campaign starts with a list. If that list includes invalid or risky addresses, delivery fails before the first email is sent. You're not just losing sends — you're risking your reputation with ISPs. A single high bounce rate from poor data can trigger automated blocklists, especially if you're using multiple sender domains or managing hundreds of thousands of contacts.

Let’s be clear: even well-intentioned sends can go wrong if the data isn’t clean. Disposable emails, role accounts like admin@ or sales@, and catch-all domains all cause false positives or high delivery failure rates. These aren’t edge cases — they’re common when lists grow unchecked. A real-time verification service like MailTester’s email checker identifies these issues before they hit your queue.

Each step directly improves inbox placement

Validating sender authentication is not optional. SPF, DKIM, and DMARC aren’t just technical details — they are trust signals that ISPs use to decide whether to accept your email. If any of them are missing or misconfigured, your message gets marked as suspicious or outright rejected.

For bulk sends, you should audit the health of your domains. Check if they’re in any public blocklists using tools like MXToolbox, and verify that sending IPs aren’t flagged. You might be surprised how often IP reputation suffers quietly until a campaign fails.

Then test your actual inbox placement. Use tools like MailTester’s inbox tester to send a real message to known inboxes and see where it lands. No simulator or score — just your email in a real user’s inbox. That’s the only way to know what’s really happening.

Finally, ensure your list is clean. Remove dead, role, and disposable addresses. Use a bulk verification tool before campaigns go live. With MailTester, you can check 100 emails for free and see real-time results — no commitment, no expiration on unused credits. This is how you build consistent deliverability, not hope.

Step 1: Validate the list with real-time verification

You must run every email address through a real-time verifier before sending. This catches syntax errors, role-based accounts like admin@ or sales@, disposable domains, and catch-all domains that accept any input—each of which harms deliverability, inflates fake open rates, and damages sender reputation. Use an API to automate it at scale.

Why real-time verification matters

Older methods like batch validation or ignoring edge cases only delay the inevitable. A single invalid or risky address can trigger blacklisting. Real-time checks simulate how actual mail servers respond—no guesswork.

  1. Integrate a real-time email verification APIConnect your email service provider (ESP) or CRM with a verification API like MailTester’s. You don’t need to pre-process every address manually—just send each one in real time during prep. This ensures you're not relying on outdated or incomplete checks.MailTester’s verification API evaluates validity, role status, and domain behavior in milliseconds, with 98.9% accuracy.
  2. Filter out syntactically invalid addressesThese include malformed formats like user@domain and domains with missing top-level extensions. They break SMTP standards and will bounce immediately. Real-time tools catch these before you send.
  3. Remove role-based and disposable emailsRole accounts (e.g. support@, info@, contact@) often aren’t monitored. They’re prone to spam filters and high bounce rates. Disposable domains (like temp-mail.org) are used for one-time signups only, never long-term engagement. Most ESPs ignore or block them.
  4. Block catch-all domainsCatch-all domains accept any address—meaning someone can send to [email protected] even if the user doesn’t exist. These inflate open rates falsely and signal poor list hygiene to inbox providers. RFC 5322 and industry best practices agree: these domains reduce sender trustworthiness.Check for this using a tool that evaluates domain behavior, not just syntax.See how MailTester handles this: bulk verification for your entire list.
  5. Prefer only high-confidence valid addressesOnly send to addresses flagged as valid with a strong confidence score. Avoid “risky” or “unknown” results, as they represent potential bounces or inbox delivery failure. Quality over quantity is the only path to consistent inbox placement.Studies show that even a 1% increase in deliverability translates to measurable revenue gains over time. Start clean.
“Sender reputation is built on consistent, clean list hygiene—not on volume.” — Industry analysis from Return Path (now Oracle Marketing Cloud), 2022

Step 2: Run bulk list verification to catch anomalies

You should process your entire email list through a bulk verification tool to expose hidden risks before sending. This step reveals invalid addresses, disposable domains, and suspicious patterns like mass role accounts—issues that silently hurt deliverability and damage sender reputation. Use real-time tools that test against SMTP, MX records, and known spam sources to catch them early.

  1. Upload your full list to a bulk verification system. This lets you scan every address at scale, finding issues you’d miss with spot checks. The goal is to see the full picture—patterns often reveal themselves only across large datasets.
  2. Look for excessive role accounts (like admin@, contact@, sales@). While not always invalid, high volumes suggest low engagement and increase bounce risk. ISPs and inbox providers flag lists with many role addresses as low quality, harming your reputation even if delivery technically succeeds.
  3. Check for disposable or free email domains. Services like Mailinator or Temp-Mail exist solely for temporary sign-ups. Including these inflates your list size with non-humans who won’t open or engage. These addresses rarely deliver and may trigger spam filters.
  4. Remove addresses marked as 'risky'. These include suspended mailboxes, abandoned accounts, or misconfigured domains. Unlike outright invalid addresses, risky ones may accept mail initially—only to bounce days later, leading to high late bounces and reputation damage.
  5. Review the results and clean your list. Keep only valid, engaged, and deliverable addresses. Use tools that report back detailed verdicts: valid, invalid, catch-all, risky, or disposable. Knowing the difference matters—some domains accept any address (catch-all), which skews engagement metrics and increases inbox placement risk.

Why this step prevents post-campaign fallout

Many teams skip bulk verification because they assume their list is clean. But real-world data shows that even well-maintained lists contain 10–15% invalid or risky addresses. Catching these before sending avoids high bounce rates, blacklists, and degraded sender reputation—common causes of campaign failure.

How to do it right

Use a tool that checks real-time SMTP responses, validates MX records, and cross-references against spam trap databases and known disposable domains. For example, MailTester’s bulk verification scans your entire list in minutes and flags anomalies with a 98.9% accuracy rate. It doesn’t just identify bad addresses—it shows you the why behind them.

Don’t rely on filters or heuristics alone. Real deliverability depends on actual sender reputation, which is built on consistent engagement and low bounce rates. Verify your list now—before you send.

Step 3: Check DNS records and authentication setup

You must verify SPF, DKIM, and DMARC records are correctly configured to prevent bounces and spam filtering. Misconfigured or missing records cause rejection even with perfect content. Use tools like MxToolbox or RFC 7001 to validate DNS entries. A single missing record can break deliverability for thousands of users.

Validate SPF: List Every Sending IP

  1. Check your SPF record to ensure it includes every IP address or range used by your ESP or sending server. SPF limits you to 10 DNS lookups; exceeding this breaks verification.
  2. Use MxToolbox’s DNS Lookup to test your domain’s SPF record in real time. Ensure it doesn’t trigger a "softfail" or "fail" during email authentication checks.
  3. Never omit your ESP’s IP range — even if it’s a third-party platform like SendGrid or Mailchimp. An incorrect or incomplete SPF allows spoofing and increases spam likelihood.

Verify DKIM and DMARC Policies

  1. Ensure DKIM is set up and signing every outgoing message. DKIM cryptographically verifies email origin and integrity. Without it, emails may be flagged or rejected.
  2. Test your DKIM signature by sending a test email and checking the header. Use RFC 6376 as reference to confirm correct domain and selector alignment.
  3. Confirm your DMARC policy (none, quarantine, or reject) is published in DNS. Set it to "reject" if you’re ready to enforce authentication. This protects your brand and improves inbox placement.
  4. Include a valid DMARC aggregate report recipient (rua) address to receive authentication failure reports. This helps detect unauthorized sending or misconfigurations.

Even with strong content, missing or mismatched DNS records increase bounce rates. According to dmarc.org, 27% of domains with no DMARC policy are spoofed within 48 hours. Let’s not be part of that.

Use MailTester’s email checker to verify individual addresses and detect misconfigured authentication early. For bulk campaigns, test your entire list with bulk verification before sending.

Step 4: Test inbox placement with real messages

Send real test emails from your domain to major inbox providers like Gmail, Outlook, and Apple Mail. Use a service like MailTester to simulate how your message routes through real-world filters. Check if it lands in Inbox, Spam, or gets blocked entirely — this reveals ISP-specific rejections even with correct headers. You’re not testing theory; you’re checking reality.

Run the real delivery test

  1. Send a test message from your sending domain to a few real addresses across Gmail, Outlook, and Apple Mail. Use a clean, non-transactional template that mirrors your campaign content. This mimics actual user behavior and triggers the same filters real subscribers see.
  2. Check delivery results across each provider. Do not rely on bounce reports alone — some emails are accepted but routed to Spam. Use tools that track real placement, not just delivery status.
  3. Use a dedicated inbox placement tester like MailTester’s Inbox Tester to send your message through multiple real mail servers and get consistent placement reports across providers. These services simulate how your content is processed in real environments.
  4. Review the results: Is your message marked spam by Gmail? Is Outlook applying filters due to header issues? Is Apple Mail quarantining it? Each ISP has unique scoring rules, and these tools surface problems that SPF/DKIM/DMARC alone won’t catch.
  5. If your email is blocked or sent to Spam, examine headers — sometimes content triggers filters even if authentication is correct. Check for red flags like suspicious links, high image-to-text ratios, or spammy sender reputation. The RFC 5322 standard defines email structure, but ISPs interpret it with behavioral models.
  6. Repeat this before every major campaign. Even if your list was clean last month, sender reputation changes, and ISPs evolve. Regular testing keeps you ahead of filter shifts.

What to look for

Even with flawless authentication, content can trigger filters. High-volume senders often miss this. For example, a single word like “guarantee” in promotional text can trigger automatic spam scoring in some systems — especially if paired with weak engagement metrics.

Use MailTester’s inbox placement test to identify provider-specific rejections. You’ll see exactly which mail service is blocking or flagging your message, and why. This is where technical accuracy meets real-world behavior.

Let’s be clear: no tool replaces actual delivery proof. But testing with a service like MailTester gives you immediate, actionable insight — not theory. That’s the difference between guessing and knowing.

Step 5: Assess sender reputation and domain age

Before sending, check your domain’s history: new domains or those with prior abuse reports are more likely to hit spam filters. Use tools like MxToolbox or Spamhaus to verify you’re not on a blocklist. A clean reputation, solid engagement, and consistent volume over time all matter more than a flawless inbox score.

Why sender reputation and domain age matter

  1. Check your domain’s blocklist status using tools like MxToolbox or Spamhaus. These services scan known spam sources and can tell you if your domain or IP has been flagged. If you’re listed, your messages risk being blocked entirely.
  2. Review your domain’s age and sending history. New domains—especially those created in the past 30–90 days—lack the trust signal that established domains have. Spam filters evaluate your domain’s age, volume, and past delivery success. Sending high volumes immediately from a new domain raises red flags.
  3. Assess engagement patterns. ISPs like Gmail and Outlook prioritize senders who maintain consistent sending volume and meaningful inbox engagement (opens, replies, low spam complaints). Sudden spiking or mass mailouts to inactive addresses erodes trust—even if the content is clean.
  4. Warm up new or flagged domains. If you’re using a new domain, start with low volume (50–100 emails/day) and gradually scale. This builds a positive delivery history. Tools like MailTester’s email checker help you validate sender address legitimacy before you even begin warming.
  5. Inspect reverse DNS and authentication records. A missing or improperly configured reverse DNS (PTR record) can undermine reputation. Ensure SPF, DKIM, and DMARC are correctly set—these signals help verify you’re the true sender.

What to watch for

High bounce rates or spam complaints, even from a single campaign, can trigger filters. If your domain was recently involved in a breach or reported for spam, wait until those signals clear. Even brief exposure can linger in spam scoring algorithms.

You’re not just sending to a list—you’re sending from an identity. That identity’s trustworthiness determines whether your message lands in the inbox or the junk folder.

Step 6: Review list hygiene thresholds for your industry

You should validate your list against industry-specific hygiene standards before sending. High-performing email campaigns maintain bounce rates under 0.5%, avoid over 10% role-based or disposable addresses, and ensure no more than 2% of addresses are invalid. These thresholds directly affect inbox placement and sender reputation. Let’s test your list against real benchmarks.

Bounce rates: Target below 0.5%

  • Most top-performing senders keep hard bounces below 0.5%—a benchmark supported by industry data from Return Path and independent deliverability studies.
  • If your list exceeds this threshold, investigate outdated data, poor capture practices, or list segmentation issues before sending.
  • Return Path (now part of Validity) has long tracked benchmark performance; consistently hitting 0.5% or lower is a strong indicator of list health.

Remove role and disposable addresses

  • Lists with more than 10% role-based (e.g., admin@, sales@) or disposable (e.g., tempmail.org) addresses show significantly lower engagement.
  • These domains are rarely opened, often flagged, and can hurt sender reputation—Spamhaus and other blocklist operators track patterns tied to such domains.
  • Verify addresses in real time with a service like MailTester’s email checker to eliminate them before campaign launch.

Keep invalid rates under 2%

  • Any list with 2% or more invalid addresses should be fully cleansed. This includes syntax errors, non-existent domains, and non-deliverable mailbox issues.
  • Even a small number of invalid addresses can trigger ISP filters, especially when sent at scale.
  • Use bulk verification to process high-volume lists and flag issues at scale—no need for manual cleanup.

Engagement is the real deliverability signal

  • Inbound engagement—opens, clicks, forwards—correlates directly with inbox placement. ISPs use this data to assess sender trustworthiness.
  • Even if bounces are low, a list with poor engagement often gets filtered or sent to spam. Clean address lists alone don’t guarantee delivery.
  • Test how your message performs in real inboxes with MailTester’s inbox placement tool before sending to live audiences.
Deliverability isn’t just about avoiding bounces—it’s about proving your list is actively engaged, and that starts with hygiene.

Step 7: Integrate verification into your ESP workflow

You can prevent bounces, protect sender reputation, and boost inbox placement by automating email verification directly within your email service provider. Use MailTester’s integrations with Mailchimp, HubSpot, Klaviyo, or SendGrid to validate lists before every send—keeping your data clean and your deliverability strong.

Build verification into your workflow

  1. Connect your ESP to MailTester using one of the native integrations at MailTester’s integrations page. This syncs your list data automatically and lets you trigger verification with a single click. No more manual CSV uploads or spreadsheet checks.
  2. Use the real-time API for pre-send scrubbing. Integrate the MailTester API into your send process so every address is validated milliseconds before delivery. This stops invalid, disposable, or role-based addresses from ever hitting the inbox, reducing bounce rates from typical 5–15% to under 2%.
  3. Set up automated triggers after data imports. Whenever you import a new list or sync contacts from CRM or a landing page tool, run verification automatically. This stops dirty data from entering your campaigns—especially important with third-party sources where address quality is unpredictable.
  4. Embed verification into onboarding flows. For new subscribers, run a quick email check during signup. This blocks fake, typo-ridden, or disposable addresses before they’re added. The result? A cleaner list from day one, with lower suppression rates and higher engagement over time.

Automated verification isn't plug-and-play—it's plug-and-scale. Once integrated, it runs silently, catching issues you won’t see in a static list. Tools like MailTester use real-time SMTP checks, MX lookups, and role account detection to assess validity at scale, matching industry standards like RFC 5321 for mail server response handling.

According to Spamhaus, consistently poor sender reputation due to invalid addresses is one of the top reasons emails land in spam folders. You’re not just cleaning data—you’re maintaining trust with inbox providers.

Start with 100 free verifications at MailTester’s pricing page, then scale as your list grows. No credit expiration, no contracts. Just a reliable system that reduces waste and strengthens deliverability from the ground up.

Step 8: Use AI to interpret verification results

You don’t need to be a DNS or SPF expert to understand why an email was flagged as “risky” or “catch-all.” MailTester’s in-app AI assistant breaks down complex verification verdicts in plain English, explains the likely reason behind each flag, and spots patterns across large lists—like repeated bad domains or shared IPs—so you can act fast without deep technical knowledge. This cuts manual review time and improves accuracy.

Decoding complex verdicts without domain expertise

Not every “invalid” address is broken—it could be a catch-all mailbox, a role account, or a temporary alias. These aren’t outright errors, but they can still hurt deliverability. Let’s say you see a batch of “catch-all” results. The AI assistant doesn’t just label it—it explains that this means the domain accepts all emails, which often triggers spam filters. It tells you why it matters (high bounce risk, poor sender reputation) and whether you should proceed or clean the list.

Spotting systemic risks across your list

When you verify thousands of addresses, manual review isn’t feasible. That’s where the AI’s pattern detection shines. It can identify clusters of problem addresses tied to a shared domain, IP range, or even a specific email provider (like a free provider often used for bots). This helps surface systemic issues—such as a large number of outdated company addresses using a deprecated domain—before they tank your sender reputation.

For real-world context, industry reports show that poor list hygiene can reduce inbox placement by up to 20% for non-critical senders. Tools like MailTester’s AI help counteract that risk by transforming raw data into actionable insights. The process is repeatable: check a list → get results → use the AI to interpret them → fix issues → verify again.

Explore how it works in practice with a bulk verification or integrate with your senders via the real-time verification API. Your inbox placement depends not just on what you send, but also on who you’re sending to—with the right tools, you can be confident both are solid.

Step 9: Maintain and monitor post-send

After sending, keep watching: track bounces and complaints in real time to catch infrastructure or list quality issues early. Use verification logs to spot long-term trends in address decay and re-verify inactive segments before you send again. This ensures your sender reputation stays clean and inbox placement remains stable.

  1. Monitor bounces and complaints in real time Bounces (hard or soft) and spam complaints directly impact your sender reputation. A single spike in complaints can trigger filtering. Use your ESP’s dashboard or a third-party tool to alert you within minutes of anomalies. The RFC 6650 defines standard bounce semantics — understand them to filter false positives.
  2. Review your verification logs monthly Over time, even clean lists degrade. Logs show when addresses go invalid, how fast decay happens, and which domains fail most often. Track this trend. If you see a steady 1–2% drop per month in active addresses, it’s likely time to re-verify.
  3. Update your sender reputation dashboard with real data Don’t rely only on reputation scores from ISPs. Feed real deliverability results back into your internal tracking. If 97% of emails land in inbox, but 1.2% of recipients report spam, that’s a warning. Use platforms like Spamhaus and MxToolbox to manually verify if your IP or domain is listed.
  4. Re-verify dormant lists before re-engagement A list of addresses that hasn’t been touched in 18+ months is likely over 30% invalid. Run a bulk verification before sending. Validating just 10,000 addresses upfront can save you 300+ bounces and reduce complaint rates by up to 40%.

Why this keeps your list alive

Without post-send monitoring, you’re flying blind. What looks like a “good” delivery rate today might hide an emerging blocklist issue or a deteriorating list. Regular validation isn’t just about cleaning — it’s about proving your list is still valid, your domain trustworthy, and your engagement signal clear.

Automation helps

Set up recurring verification jobs via the verification API. You can automate quarterly re-validations or trigger new checks when a campaign fails. This keeps your database fresh and reduces the risk of sender reputation degradation during large outreach cycles.

The 98.9% accuracy of MailTester’s verification

You can trust MailTester’s verification to identify valid, invalid, catch-all, and risky email addresses with 98.9% accuracy—meaning you’re not just filtering out bad addresses, you’re preserving the ones that matter. This precision cuts down on false positives, so you don’t lose valid subscribers to overzealous cleansing.

How high accuracy is actually achieved

Unlike tools that rely on incomplete pattern matching or third-party databases, MailTester performs over 250 checks per email address. It validates at the SMTP protocol level, testing whether the domain’s mail server will accept messages for a specific address. This isn’t guesswork—it’s real-time, end-to-end validation.

It checks MX records, domain existence, syntax, role accounts, disposable domains, greylisting behavior, and more. Every flag is grounded in actual server responses, not heuristics. This approach avoids misleading results, especially with catch-all accounts that accept all emails but don’t represent active users.

Why accuracy matters for deliverability

A single bad address can hurt your sender reputation, especially if it triggers bounces or complaints. With MailTester’s 98.9% accuracy, you reduce the risk of sending to invalid or risky addresses before a campaign even launches.

Many tools claim high accuracy but use outdated data or incomplete validation. MailTester’s approach is transparent: it doesn’t guess. It connects to the actual server, simulates a real send, and reports back based on what’s returned. This is how you achieve reliable results that align with industry standards—like those outlined in RFC 5321 and RFC 5322 for email structure and delivery.

Want to test your list before sending? Try our bulk email verification tool. It’s designed for teams that need real confidence in their send. The 98.9% accuracy isn’t a marketing claim—it’s the result of a system built to validate email addresses at the network level, not the guesswork level.

Conclusion: Deliverability is a technical foundation, not luck

Pre-campaign deliverability validation isn’t a nice-to-have. It’s a requirement. Without it, deliverability depends on chance, not control.

Every email sent must be verified for syntax, authentication, and inbox placement. Skipping any step risks bounces, blocklists, and wasted sends.

The best email service providers don’t leave deliverability to chance. They enforce technical quality with real-time verification, domain authentication, and testing across inboxes.

Sources

Keep reading

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Frequently asked questions

What is the difference between email verification and deliverability testing?

Email verification checks if an address is valid and real. Deliverability testing confirms whether the message will land in the inbox across major email providers.

How does MailTester achieve 98.9% accuracy?

It performs full SMTP-level validation and cross-references real-time infrastructure data, including DNS records and blacklists, across multiple test points.

Can I use MailTester with SendGrid or Mailchimp?

Yes. MailTester integrates directly with SendGrid, Mailchimp, HubSpot, and Klaviyo to automate list verification before sending.

What does 'risky' mean in an email verification verdict?

A 'risky' verdict indicates an address that may be valid but has signs of low engagement, outdated status, or technical flaws that harm deliverability.

Why should I verify before sending even if I have double opt-in?

Double opt-in prevents new signups from being fake, but existing lists degrade over time — addresses become invalid, role-based, or disposable.

What’s the best way to test inbox placement?

Use real-world inbox placement testing with a tool like MailTester that sends actual messages through real servers to Gmail, Outlook, and Apple Mail.

What’s the impact of catch-all domains on deliverability?

Catch-alls accept any email, even non-existent ones. This inflates bounce rates and suggests spam behavior, harming sender reputation.

How do role accounts affect deliverability?

Role accounts (e.g. sales@, support@) are often used for bulk or promotional emails. Email providers treat them as low-engagement, increasing spam risk.

Do purchased credits expire with MailTester?

No — all purchased credits never expire, giving you flexibility to use them when needed.

What if my sender domain is new?

New domains must be warmed up. Start small, build sending history, and verify authenticity before scaling volume.

How often should I clean my list?

Verify your list before each campaign and refresh monthly to remove outdated or inactive addresses.

Can I automate pre-campaign validation?

Yes. MailTester’s API and integrations with Mailchimp, SendGrid, HubSpot, and Klaviyo allow full automation of list checks before each send.