The common mail protocols for mail client to server and server to server communications are Post Office Protocol version 3 (POP3), Simple Mail Transfer Protocol (SMTP) and Internet Message Access Protocol version 4 (IMAP4).
Another common method for accessing e-mails is web access to mail, in which you have common mail servers such as Gmail, Yahoo!, and Hotmail. Some examples include Outlook Web Access (OWA) and RPC over HTTPS for the Outlook web client from Microsoft and others.
In this recipe, we will talk about the most common client-server and server-server protocols: POP3 and SMTP. We will also look at some typical problems by using the other methods.