One of my websites has a weird problem sending a contactform, when I migrate this website from a ubuntu server to a centos (6.x) server. A message send with the form of his website does not receive the external mailserver.
Yes, I use Virtualmin, without mail, which is running on a external server. I have Postfix running for website forms and within Ubuntu is worked fine, but it doesn't in Centos. The strange thing is dat joomla! and wordpress forms working OK, but this one not.
This is the mail system at host vm3.hostingserver.com.
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
<firstname.lastname@example.org>: User unknown in virtual alias table
I think it is an internal error of postfix, but how can I get postfix running to the email@example.com, which is running outside the webserver?