Answer
POP before SMTP is a means of allowing an external user to use your mail server to send external email if and only if they have been authenticated by the POP service on your server first. It does not matter what IP address they use providing they can be authenticated by username and password.
Once the user has been successfully validated, their IP address is temporarily seen as “local” and thus the user will now be able to use your server as an outgoing mail relay.
The user connecting with this IP is able to relay mail for a time period setup by the administrator.
By default GMS Mail does not allow relay and to use this option requires GMS Anti-Spam.
To enable POP/IMAP before SMTP from within GMS Anti-Spam you will need to check a server side setting.
From the admin interface, navigate to the system level Anti Spam node, expand Bypasses and click on Authenticated Clients. Ensure that either “Allow relay but perform other checks” or “Bypass all anti-spam checks” is enabled. “Normal anti-spam checks” will mean this authentication mechanism is disabled.
See Also:
- How do I allow external users to relay mail through my server?
- What is IMAP before SMTP?
- Can I provide secure access to email?
Keywords:POP SMTP authentication relay remote users JUCE Spam checker GMS Anti-spam anti spam antispam