My company hosts its own email server running Exchange 5.5. Our ISP feeds our mail directly to us via ISDN connection.
Some of my outgoing email bounces back from the outside with an “unable to deliver message due to comm. failure, 554 buildaddr: unknown mailer emstp”.
I also have some sites that can’t send to us.
I can’t find the cause of this error code, or how to resolve the problem.
Any suggestions would be appreciated.
