Your request (mail delivery failed) couldn't be recognized!

[Kurieuo]

Hi,

I have received 1000's of the following emails directed to [email protected] from [email protected]. I am confused why the recipient is the mailer-daemon. The subject of the email is "Your request (mail delivery failed) couldn't be recognized!" and body "Your request was not processed. Please try again."

The particular domain sent from is specifically used by a client hosted on my server to send email to authentic mailing lists. They recently began using SMTP to send email, so not sure if that has something to do with it. I am concerned as to whether the real emails are failing due to something I have configured on the server whether it be Exim rules, cPanel tweaking settings, CSF or other. If anyone knows why these emails are happening I would greatly appreciate any information provided.

Thanks!

 

[chirpy]

Emails usually end up at mailer-daemon as a last resort destination because delivery could not be achieved. This is part of the SMTP protocol where it always attempts to let someone know that an email delivery failed (mailer-daemon on the local server being the last place it will try). The content of the email headers within the mailer-daemon mail is what you have to work on to establish why the emails are not being delivered.

 

[Kurieuo]

Thanks chirpy.

I do not know for sure why 4000+ emails failed, however your saying it tries to let someone on the server know an email delivery failed made me think the sender email address was an invalid email if mailer-daemon was receiving the failures.

Sure enough I checked the email addresses setup for the hosted domain which sent out the emails, the the email address being sent from did not exist. Perhaps the sender email address could not be authenticated as a valid email address on the server and this is why the emails failed to send??

In any case, the client should now receive their own failed emails.