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POP3S in the TCP / IP protocol stack :
application POP3
transport SSL / TLS
Internet IP ( IPv4 , IPv6 )
Network access Ethernet Token
FDDI ...

POP3S is the name of a network protocol for expanding the POP3 e-mail transmission protocol to include encryption using SSL / TLS . Usually TCP on port 995 is used for POP3S .

An alternative is to use POP3 with STARTTLS for encryption. The communication takes place on the standard port 110. In this case, however, the encryption can be switched off unnoticed by the user when the connection is established, provided the client does not force it.

Web links

  • RFC 2595 - Using TLS with IMAP, POP3 and ACAP

Individual evidence

  1. RFC 3207 - SMTP Service Extension for Secure SMTP over Transport Layer Security . "The SMTP client and server may decide to move ahead even if the TLS negotiation ended with no authentication and / or no privacy ..."