Standard Email Ports and Protocols
-
Email uses a series of protocols for different functions. And it has become common to use multiple ports for each protocol. Some ports are dual purpose, generally allow insecure and secure via STARTTLS connections, and others are assumed to be SSL explicit. No ports are necessarily insecure and all insecure ports can be configured to require STARTTLS.
SMTP is the MTA protocol. POP3 and IMAP4 are the MDA protocols.
Protocol Security Port SMTP Clear or STARTTLS 25 SMTPS SSL 465 SMTP STARTTLS 587 POP3 Clear or STARTTLS 110 POP3S SSL 995 IMAP4 Clear or STARTTLS 143 IMAPS SSL 993
