sendmail: trusted-users or aliases?

Question

For a project that I have been assigned to, I need to send emails to a business partner (business_partner.com) 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. me@hidden_domain_name.com) to send these notifications. Instead, it uses an intranet email address (the server's where my code resides: user_name@servername.hidden_domain_name.com).

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?

Answer 1

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: http://www.mxtoolbox.com/diagnostic.aspx

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.