DNS is used to translate human-readable names to IP addresses.
The actual translation is done by DNS servers who communicate with eachother in a hierarchical way.
A name which is registered on the Internet, e.g. mycompany.com
A name for a computer on the Internet. The last part of the complete hostname is the domain name, e.g. mail.mycompany.com
A hostname can be translated to an IP address by a DNS server.
IMAP is a protocol that allows mail clients to retrieve mail from a mailbox on a mail server.
IMAP is a bit more advanced than POP3. It allows a mailbox to have several subfolders, and it also allows a mail client to receive a list of the mails without having to download the actial mails themselves.
Every machine connected to a TCP/IP network (like Internet) has a unique number, i.e. an IP address.
Entry in DNS server that specifies which server is responsible for a certain domain.
POP3 is a protocol that allows mail clients to retrieve mail from a mailbox on a mail server.
SMTP is the protocol mail servers use to communicate with eachother.
Mail clients also use SMTP for sending mails.
This is the network protocol used by the Internet.