Google Workspace SMTP relay rejects email notifications because Kopia sends EHLO localhost

Description

Email notifications fail when using Google Workspace SMTP Relay on port 587 without authentication.

Kopia reports:

Error sending notification: unable to send notification: unable to send notification message: EOF

Environment

• Kopia: 0.23.1
• OS: Windows 11
• Running as: Windows service under LocalSystem
• Configuration: WebUI
• SMTP server: smtp-relay.gmail.com
• Port: 587
• Username/password/identity: Blank
• Authentication: Google IP-based SMTP relay

Troubleshooting

Sending a complete test email with curl.exe succeeds from the same computer under both:

• Interactive user
• LocalSystem

TCP 587 and STARTTLS also work correctly.

A newly created Kopia notification profile produces the same EOF error.

Manual SMTP testing shows that Google rejects EHLO localhost:

C: EHLO localhost
S: 421-4.7.0 Try again later, closing connection. (EHLO)

Google accepts the actual computer hostname:

C: EHLO PC0179
S: 250-smtp-relay.gmail.com at your service
S: 250-STARTTLS

It appears that Kopia's SMTP connection identifies itself as localhost. Google then closes the connection, which may result in the EOF error shown by Kopia.