465
Encrypted email submission via implicit TLS (SMTPS)
SMTP over TLS (SMTPS / SMTP SSL)
What is port 465?
Port 465 is used for SMTP email submission with implicit TLS encryption — the TLS handshake occurs immediately upon connection. Originally deprecated by IANA, it was officially reinstated by RFC 8314 as the preferred port for email clients that submit outgoing mail. Major providers including Gmail and Outlook support it. The alternative is port 587 with STARTTLS upgrade.
Quick checks
$
nc -zv example.com 465
$
nmap -p 465 example.com
$
telnet example.com 465