How to solve “550 sorry, user unknown” problem when using pd-admin

Recently, a client reported problems when trying to send mail to certain domains hosted on their own web server. The web server in question was running pd-admin as administration tool set. Mail hosting was done on a separate dedicated mail server. The error message reported by the client was the infamous

550 sorry, user unknown

Checking SMTP through telnet

Having a quick look at the pd-admin (web server) and qmail configuration (mail server) did not reveal any errors in the setup. Thus, a quick telnet check for the email account in question was done to make sure the SMTP service was operating normally:

COMMAND:
telnet mx1.company.com 25
RESPONSE:
Connected to mx1.company.com.
Escape character is ‘^]’.
220 mx1.company.com ESMTP

COMMAND:
helo hi
RESPONSE:
250 mx1.company.com

COMMAND:
mail from: <your-email@gmail.com>
RESPONSE:
250 2.1.0 Ok

COMMAND:
rcpt to: <user.in.question@company.com>
RESPONSE:
550 5.1.1 <user.in.question@company.com>: Recipient address rejected: User unknown in virtual alias table

COMMAND:
quit
RESPONSE:
221 2.0.0 Bye

This check was done on the troubled web server itself. It seemed like that the MX record was pointing to the web server itself and not the mail server.

The solution

When creating customer accounts and setting up domains through pd-admin it automatically creates MX records for these domains too (although the mail server option was not selected during the domain setup on the web server). In case you want to get rid of these MX records

  • navigate to Customers

pd-admin-customers

  • select Overview and select the Domain option for the customer in question

pd-admin-customers-overview

  • then select the MX option

pd-admin-customers-mx

  • and finally deactivate the MX record

pd-admin-customers-mx-off   That should solve it! Yes, a pretty simple solution 😉

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