Question : 530 authentication required for relay from one sender/company

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.


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?

Answer : 530 authentication required for relay from one sender/company

Unless they can prove it is YOUR server that is failing to allow the connection then it is nothing to do with you. The message is being rejected on the first hop, so if they are using a smart host to send email (for example through their ISP) then it is that server that is rejecting the message.

Simon.