Port 465 (SMTPS (submission over TLS))

Mail submission with implicit TLS: the TLS handshake starts immediately, no STARTTLS. RFC 8314 recommends it over 587 for clients.

Well-known (system) port, 0-1023 TCP Email Meant to face the internet

What port 465 is used for

Mail submission with implicit TLS: the TLS handshake starts immediately, no STARTTLS. RFC 8314 recommends it over 587 for clients.

Security: should port 465 be open?

Meant to face the internet. Same rules as 587: require authentication, enforce strong passwords or app passwords, and watch for credential stuffing.

IANA assignment

Service nameProtoDescriptionAssigneeReference

urd TCP URL Rendezvous Directory for SSM Toerless Eckert -

submissions TCP Message Submission over TLS protocol IESG RFC 8314

igmpv3lite UDP IGMP over UDP for SSM Toerless Eckert -

Registry dates for this port: registered 2017-12-12.

Check what is listening on port 465

Linux: is anything listening on TCP 465?

sudo ss -tlnp 'sport = :465'

Linux / macOS: which process owns the port

sudo lsof -nP -i :465

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':465 '

Windows (Command Prompt)

netstat -ano | findstr :465

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 465 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine

nc -vz -w 5 HOST 465

From Windows

Test-NetConnection HOST -Port 465

Open port 465 in the firewall

ufw

sudo ufw allow 465/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 465 -j ACCEPT

nftables

sudo nft add rule inet filter input tcp dport 465 accept

Windows Firewall

New-NetFirewallRule -DisplayName 'Allow TCP 465' -Direction Inbound -Protocol TCP -LocalPort 465 -Action Allow

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.