“550 5.7.1 Unable to relay for UserX@NewDomain.com” after you added an additional domain to receive emails in Exchange 2003 Server


When you want to receive emails with new domain name (Or additional domain name) on your Exchange 2003 platform you usually create a new recipient policy (see link here: Configuring Exchange to receive mail for multiple domains). I did that and mails were bounced from Internet with 550 5.7.1 Unable to relay for .. error message. Telnetting from Internet gets the same error message after “RCPT TO:UserX@NewDomain.com” command.

Here the kicker. Sending mails internally with new domain name (UserX@newDomain.com) worked beautifully.  Mail coming from Internet were not working.  After some research, I found IIS Meta data on the Exchange mail gateway or front end server weren’t updated with new domain name for strange reason.

To check this happened to you or not, follow the steps below.

  1. Download IIS 6 resource kit tool here: iis60rkt.exe
  2. Install this on the Exchange Front-end or Mail gateway server where you receive mails from Internet. Choose Custom install and select only Metabase Explorer version 1.6.
  3. After the installation, click ”Start”->”All Programs”->”IIS Resources”->”Metabase Explorer”->”Metabase Explorer”
  4. In the Metabase Explorer, Select “LM” and Expand the tree. Right-click ”LM” and select ”Export to file”. Export the key to a mbk file for backup purpose.
  5. Navigate to LMSmtpSvc1Domain. For a normal Exchange server, you should see the second domain name under this key. If you don’t have, you need to manually add one key for the second domain.
    • Right-click the key of primary SMTP domain, choose ”Copy”.
    • Then, right-click ”Domain” and choose ”Paste”.
    • In the key already exists box, select ”Copy to a new key” and input the second domain name in the box. Click ”OK” and then you will see a new key with the second SMTP domain name.
  6. Close Metabase Explorer. Click ”Start”->”Run”->Input ”IISReset”  and press Enter.

Hope this helps you. if it is, leave me a comment here.

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11 thoughts on ““550 5.7.1 Unable to relay for UserX@NewDomain.com” after you added an additional domain to receive emails in Exchange 2003 Server

      1. It just saved me a 3rd time lol. I favorited it last time, but I switched PCs and I guess I didn’t save my favorites…I wasn’t sure it was exactly the same article until I saw my own comment up there 🙂

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