Email Ports Tutorial

What are the port numbers for the incoming and outgoing email protocols

Here is a table with the port numbers for the incoming and outgoing email protocols, both with encryption and without encryption, and a few notes on the subject. You need to know the correct port numbers when setting up an email client.

Email Port Numbers

The encryption protocols installed on the HostKnox servers are SSL3 (version 3) and TLSv1 (version 1). SSL3 (Secure Sockets Layer) is the last version of the SSL protocol. TLS (Transport Layer Security) is a newer protocol that provides better security.

In most email clients you don't have the option to select specifically whether to use SSL or TLS. There is either a single SSL (or SSL/TLS) checkbox or a drop-down menu from which you can select a single option that combines SSL/TLS. In practice, however, TLS will be used to encrypt the data transfer. Even with email clients in which you have the option to choose TLS or SSL (e.g. Outlook 2007, Outlook 2010), if you select SSL, still TLS will be used as an encryption protocol.

So, whatever the available options, you can safely select SSL and change the port number to 465 for outgoing (SMTP) and 993 for IMAP, or 995 for POP3.

Another thing worth mentioning is that with some email clients, such as Outlook 2007 and Outlook 2010, in which you can select whether to use SSL or TLS for the outgoing (SMTP) server and for IMAP incoming, the encryption port numbers 465 and 993 respectively will not work if you select TLS. In this case (with TLS selected) use the port numbers 587 and 143. The connection will still be encrypted thanks to STARTTLS. STARTTLS is actually a command to start TLS. It is used when the connection is established without encryption on the regular ports (587, 143) and with the command it's upgraded to an encrypted connection.

This is an example taken from configuring Outlook 2007 and 2010 in particular. Most email clients don't offer you the opportunity to choose between SSL and TLS, and even if you can choose, the result will be the same regardless of whether you select TLS or SSL: TLS will be used to encrypt the data transfer.

Another similar example is with Mozilla Thunderbird. There you have the opportunity to choose between SSL/TLS (combined in one option) and STARTTLS. If you select SSL/TLS use the port number for encrypted connection (465, 993, 995). If you select STARTTLS use the port numbers for non-encrypted connection (587, 143, 110). Again, in both cases the connection will be encrypted with TLS.