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Port 465 · TCP

Port 465: SMTP over TLS (mail sending)

Sending email from a mail app to your provider, encrypted from the first byte.

Protocol
TCP
On Windows
Not part of Windows; installed software uses it
Risk if open to the internet
Low

Seeing it on your PC

A mail app connecting out to 465 is sending mail.

Should you block it?

Outgoing is fine for a mail app. Anything else sending on 465 deserves a look.

Check it on your PC

Run this in PowerShell to see what is using port 465 right now, and which program owns it:

Get-NetTCPConnection -LocalPort 465 -ErrorAction SilentlyContinue | Select-Object LocalAddress,LocalPort,RemoteAddress,RemotePort,State,@{n='Process';e={(Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue).ProcessName}}

No output means nothing is using the port at the moment. For every connection at once, paste netstat -ano into the netstat explainer.

Block it in Windows Firewall

In PowerShell run as administrator, this stops other computers from connecting to this port on your PC. It does not stop your own programs connecting out.

New-NetFirewallRule -DisplayName "Block inbound TCP 465" -Direction Inbound -Protocol TCP -LocalPort 465 -Action Block

Undo it with Remove-NetFirewallRule -DisplayName "Block inbound …", using the same name. If you depend on the service on your local network, this rule stops that too.