mailer deamon - postfix error

Good day,

I have 2 domains assigned, one is the the main domain which is called for the sake of an example and the other one is called

the issue that I am facing is that if I am sending an e-mail to a mailer daemon message comes up that says:

This is the mail system at host

I’m sorry to have to inform you that your message could not
be delivered to one or more recipients. It’s attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

               The mail system (expanded from User unknown in virtual alias table

Final-Recipient: rfc822;
Original-Recipient: rfc822;
Action: failed
Status: 5.1.1
Diagnostic-Code: X-Postfix; User unknown in virtual alias table

What I have tried to do was to get rid of the mail services so I can use the php mail function and send e-mails from a web form. Previously everything was working great. After that I add back the mail, anivirus and spam services to but now I am receiving the above error.

Kindly help me to correct the issue so I can receive back the e-mails to

All the domain names are just for the sake of example, removing the real domain names.




Hrm, this is a bit of a shot in the dark – but what is your server’s hostname?

Does it happen to be “”?

If so, try changing your hostname to something else (an FQDN such as “”), and see if that resolves the issue you’re seeing.


Hi Eric,

The hostname of the server is called “web-server-home”

“user”@web-server-home:~$ hostname



Hostname should be FQDN, so you can use domain.tld but usually practice is hostname.domain.tld where hostname can be something else e.g. server1.

Hi Diabolico,

I changed the name and it didn’t help. Finally I saved what the websites, reinstall the virtual ubuntu server and everything get back to normal.

Thanks both for your time and help.