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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:

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?

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up vote 1 down vote accepted

The first thing I would do is make sure that it is not blacklisted by any other list:

Which server caused this report: "The server rejected the sender's email address"? Your sending server, or the recipient's server?

I suspect the recipient's as most likely, and if so, you are being tagged as SPAM or as an unreliable sender. The common causes of that are content, so send something with a body; lack of a PTR record; or being blacklisted.

You may also want to look into adding a SPF DNS record, which is used by some systems to verify that you are OK to send.

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