Incoming

Outgoing

POP3 versus IMAP

Simple Mail Transfer Protocol (SMTP) is the protocol used for sending emails.  Post Office Protocol 3 (POP3) and Internet Message Access Protocol (IMAP) are two different protocols (methods) used to access email.  When using POP3 your email program will check with the mail server every 5 minutes or so to see if there is new email.  Your email program will then download all new email from the mail server to the mail program.   When using IMAP however, your email program will leave all email on the mail server and simply provide you with a representation of your mailbox instead.  Of the two, IMAP is the better option – and the recommended option – when you need to check your emails from multiple devices, such as a work laptop, a home computer, or a tablet, smartphone, or other mobile device.  When using IMAP, your email program will present you with the contents of your mailbox without removing data from the mail server in the process.

SSL/TLS vs STARTTLS

We recognize the following protocols and ports:

• IMAP uses port 143, but SSL/TLS encrypted IMAP uses port 993.
• POP uses port 110, but SSL/TLS encrypted POP uses port 995.
• SMTP uses port 25, but SSL/TLS encrypted SMTP uses port 465.

STARTTLS was used to inform email clients still connecting on the ‘plain text’ ports that encrypted communication using SSL/TLS is available on dedicated ports.

The defacto standard these days is to block ports 110, 143, 25, 995 and only allow:

• SSL/TLS encrypted IMAP on port 993.
• SSL/TLS encrypted SMTP on port 465.