Here I have an Exchange server 2003. This server has been configured the default SMTP connector to send and receive emails. This connector successfully sends emails to almost all email address; but, it is not working for one specific email - in this case, the email is not delivered and the error message is the following:
5.7.1 smtp;530 5.7.1 Relaying not allowed without prior authentication: firstname.lastname@example.org
I have tested the delivery from my server to the destiny using smtpdiag.exe and if I run it with the parameter
/v, the aditional error shown is:
The server rejected the sender's email address
This IP had been in black lists before, but right now it is not reported in spamhaus. Any suggestions?