eMails with - SMTP, POP, IMAP, MAPI, unencrypted or encrypted with SSL or TLS

While refreshing my own understanding of mail authentication, I stumbled across two well written and clearly explained articles on:

SSL vs TLS: https://luxsci.com/blog/ssl-versus-tls-whats-the-difference.html

Three ways a mail message can be handled:

·         Unsecured - no encryption (no SSL or TLS)

·         Explicit (port based) encryption (SSL)

·         Implicit (by protocol) encryption (TLS)

and

SMTP TLS: https://luxsci.com/blog/smtp-tls-all-about-secure-email-delivery-over-tls.html

The sending computer or server could be configured for:

1. No TLS — never use it.
2. Opportunistic TLS — use it if it is available, if not, send insecurely.
3. Forced TLS — use TLS or do not deliver the email at all

And for the record, while there are other mail protocols, the majority of our world will use one of four:

POP(3) (Receiving email)

• Port 110 - this is the default POP3 non-encrypted port
• Port 995 - this is the port you need to use if you want to connect using POP3 securely

IMAP (Interacting with remote email stores)

• Port 143 - this is the default IMAP non-encrypted port
• Port 993 - this is the port you need to use if you want to connect using IMAP securely

SMTP (Sending email)

• Port 25 - this is the default SMTP non-encrypted port
• Port 465 - this is the port used, if you want to send messages using SMTP securely
• Port 578 - Authenticated SMTP 

Exchange MAPI

MAPI is a way for applications and email clients to communicate with Microsoft Exchange servers,

and is capable of IMAP style syncing of emails, contacts, calendars, and other features, all tied into local email clients or applications.

This function of syncing emails is branded by Microsoft as “Exchange ActiveSync.”

• RPC - this is the default SMTP non-encrypted port

(TCP End Point Mapper port (TCP/135) and the dynamic RPC port range (6005-59530) for outgoing connections)

HTTP/HTTPS

                If using webmail clients but these already have the underlying POP or IMAP running between the mail server and the webmail (http) server

Exchange 2013 default ports

 

Other related links
Exch 2013 ports 
Exch receiver security settings
Outlook settings for POP and IMAP access for Office 365 for business or Microsoft Exchange