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