Email authentication: SPF, DKIM, DMARC, BIMI and MTA-STS
In-Reply-To and References Headers for Threading in Gmail and Outlook
Learn how In-Reply-To and References headers enable threaded email communication in Gmail and Outlook.
Category
email-header-hygiene
8 posts
Email authentication: SPF, DKIM, DMARC, BIMI and MTA-STS
Mastering List-Id and List-Post Headers for Mailing Lists
Use List-Id and List-Post headers correctly to improve mailing list deliverability, reduce spam flags, and ensure your newsletters land in inboxes.
Email authentication: SPF, DKIM, DMARC, BIMI and MTA-STS
X-Auto-Response-Suppress Header for Microsoft Auto Replies 2026
Stop unwanted auto responses in Outlook. Learn how the X-Auto-Response-Suppress header works, when to use it, and how to verify email addresses that.
Email authentication: SPF, DKIM, DMARC, BIMI and MTA-STS
Auto-Submitted Header for Automated Notifications and Loops
Learn how the Auto-Submitted header prevents email loops in automated notifications. Use MailTester to verify email addresses and avoid delivery issues.
Email authentication: SPF, DKIM, DMARC, BIMI and MTA-STS
Precedence Bulk Header Purpose and Modern Relevance in 2026
Learn the true purpose of the Precedence bulk header and why it still matters for email deliverability and list hygiene in 2026.
Email authentication: SPF, DKIM, DMARC, BIMI and MTA-STS
Fix Date Header Timezone Errors and Future Dated Emails Flagged
Stop future-dated emails and timezone errors from harming deliverability. Use MailTester to verify and correct email headers before sending.
Email authentication: SPF, DKIM, DMARC, BIMI and MTA-STS
Missing or Duplicate Message-ID Causing Spam Filtering
Fix email delivery problems caused by missing or duplicate Message-ID headers. Use real-time verification and inbox placement testing to catch issues.
Email authentication: SPF, DKIM, DMARC, BIMI and MTA-STS
Message-ID Header Format Requirements and Uniqueness Rules in 2026
Ensure your emails comply with Message-ID format requirements and uniqueness rules. Verify headers, prevent delivery issues, and improve inbox placement with ac