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We are sending email using smtp port 25 in a local Exchange 2010 server We do not set username nor passwords in the SMTP connection, only "form" address. Mails are sent to external recipients after the Exchange enabled our server as an anonymous mail source.

However when the recipient does not exists the sender (the mail in the from: field of the mail header) doesn't get an NDR to his mailbox.

When trying to send email to the same recipient from outlook using native exchange protocol the sender get NDR to his mailbox.

Is it possible to enable the sender to receive NDR when sending emails to external address with SMTP Port 25 anonymously (however the "from" field has a valid email in it) ?

If not what is the best practice to accomplish it, considering we send email using SMTP on port 25 with no SSL

  • How exactly are you sending these emails from local Exchange to this invalid email address? Are you doing this from TELNET command prompt with SMTP commands or some other tool to run SMTP commands? I think it's the hub transport rules that should have the option for NDR without looking though. In any case, I understand when you send from Outlook it follows your Exchange rules but how are you doing this from your local Exchange as you state exactly, I'm confused by this part of your question. – Pimp Juice IT Jan 26 '16 at 22:56
  • Hi, and thank you for your reply We use a Perl script to send email from an application. Most of the time it works but from time to time the users use outdated email address and because they don't get NDR to the mailbox they don't know the send actually failed – Roeya Jan 27 '16 at 5:12
  • @Roeya Are you able to telnet from the server where you're running the perl script? Does telnet with similar attributes result in NDR? I am just wondering if caused by how the perl script is written. Typically, telnet to an invalid address while the "from" address is valid, should result in NDR – Lex Feb 23 '16 at 17:27

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