I'm using sendmail with spamassasin, one of my server is working behing it. All the port 25 traffic for the server behind it is being filtered.

User are using smtp authentication enabled in Microsoft outlook 2007 or 2010. All user has to face error "none of the authentication methods are supported by your server".

Is there any way that i could filter spam in bridging without breaking authentication?

Scenario: sendmail+spamassain (inbridge)--> MailServer