One company attempting to email us is getting an intermittent bounceback
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<c249.servername.LOCAL #5.5.0 smtp;530 authentication required for relay (#5.7.1)>
I'm not sure what their email system is but we're running exchange 2003. I'm guessing this is an issue on their end because I'm not sure whey they would be attempting to relay through us, or it is an issue somewhere between them and us. The server name in the error (c249.servername.local) is just their local server reporting the error, not necessarily the server that is denying the relay correct? Also, is there some way to see if our server is the one possibly denying the relay, or to setup logging so that I can prove that their message isn't even getting to us when it bounces back, and hence we are not the ones denying the relay?