Email Protocols

Email Protocols

There 3 types of mail protocols that are used on our mail server. POP and IMAP for the receiving of email and SMTP for the sending of email. Below you will find the description for each protocol as well as the values you will need to connect to our mailserver.


POP/POP3 Incoming Server:

995 (SSL) Normal password

110 (STARTTLS or TLS) Encrypted password

POP is the older design, and hails from an era when intermittent connection via modem (dial-up) was the norm.  POP allows users to retrieve email when connected, and then act on the retrieved messages without needing to stay “on-line.”  This is an important benefit when connection charges are expensive.

The basic POP procedure is to retrieve all inbound messages for storage on the client, delete them on server, and then disconnect.  (The email server functions like a mailbox at the Post Office — a temporary holding area until mail gets to its final destination, your computer.)

Outbound mail is generated on the client, and held for transmission to the email server until the next time the user’s connection is active.  After it’s uploaded, the server forwards the outgoing mail to other email servers, until it reaches its final destination.

Most POP clients also provide an option to leave copies of email on the server.  In this case, messages are only removed from the server when greater than a certain “age” or when they have been explicitly deleted on the client.  It’s the copies on the client that are considered the “real” ones, however, with those left on the server merely temporary backups. *IMPORTANT to note that leaving copies on the server means that your storage space is being used by this method and if not properly managed you could exceed the storage you have available in your STN plan.


IMAP Incoming Server:

993 (SSL) Encrypted password

143 (STARTTLS or TLS) Encrypted password

IMAP is the newer protocol and oriented toward a “connected” mode of operation.  The standard IMAP procedure is to leave messages on the server instead of retrieving copies, so email is only accessible when “on-line.”

IMAP is more suited to a world of always-on connections, particularly the fast connections offered by broadband mechanisms.  Having to be connected to read your email is a trivial obstacle when the connection is always available.  (It’s a little like leaving your messages at the Post Office, and going there every time you want to read them.  That might be difficult in the physical world, but it’s easy in the virtual one.)

Because messages remain on the server, until explicitly deleted by the user, they can be accessed by multiple client computers — an important advantage when you use more than one computer to check your email.

IMAP does not preclude keeping copies on the client, but, in an inversion of the way POP works, it’s the server’s copies that are considered the “real” ones.  That offers an important security benefit — you won’t lose your email if, for some reason, your client computer’s storage media fails.

*IMPORTANT to note that because IMAP leaves emails on the server this means that your storage space is being used by this method and if not properly managed you could exceed the storage you have available in your STN plan.


SMTP Outgoing Server:

465 (SSL)


At the risk of overloading you with information, you should know that strictly speaking it’s only the incoming mail that is handled by a POP or IMAP protocol.  Outgoing mail for both POP and IMAP clients uses the Simple Mail Transfer Protocol (SMTP).

When you set up a POP or IMAP email account on email client software, you must specify the name of the (POP or IMAP) mail server computer for incoming mail (  You must also specify the name of the (SMTP) server computer for outgoing mail (  Depending on the client, there may also be specifications for email directories and searching.

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