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For a project that I have been assigned to, I need to send emails to a business partner ( from one production server. However, my emails neither reach their destination nor bounce back to me ("reject: MAIL from unknown").

Further analysis by my IT support shows that emails are successfully sent out ("Message accepted for delivery").

The app I coded is not using a public internet email address (e.g. to send these notifications. Instead, it uses an intranet email address (the server's where my code resides:

My IT support guys believe it is the cause of the problem.

We created an alias but it made no change. Would adding my public internet email address to "trusted-users" file (we use sendmail) help?

How can I solve this?

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up vote 1 down vote accepted

It is probably because when you e-mail, your e-mail server announces, who it is. The receiving server then does a reverse DNS check by comparing the name of the server your e-mail server announced with the PTR (reverse DNS record) of the IP addresses the inbound mail is coming from. If they do not match, many e-mail servers just drop them without any bounce messages.

I would suggest that you go test it here:

If you do not hae a PTR record, you have two choices:

  1. Get your ISP to add it.
  2. Use a smarthost to relay mail through.
share|improve this answer
Mmm...makes sense to me. I did not include snapshots of my maillogs but it seems to confirm with you stated. I believe sendmail can work with a smarthost. I'll look into it. – Chris Jul 27 '11 at 18:33
Accepted your answer. Although I could not vote it up since I have only 8 rep. – Chris Jul 27 '11 at 18:41
@Chris Thank you very much. I am maxed for today with upvotes anyway, so I only get the points for marking anyway, so that was great. I really appreciate it. – KCotreau Jul 27 '11 at 18:43

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