I have been trying to set up virtual domains under apache and also figuring out postfix's virtual mailbox domains.

I found a howto about it and followed the directions to setup a mysql database to record the hosted domains and users, postfix to handle the delivery, and courier-imap to serve the mail out to the end users.

This was made simpler by the Postfix Admin webtool (php), but now it seems that I can't create the actual mailbox directories using the script.

The script actually calls fsockopen, which attempts to send a bogus email to the local account by manually opening a SMTP transaction on localhost port 25, normally resulting in postfix automatically creating the corresponding mail directory (/usr/local/virtual/domain.com/user).

Now, the fsockopen seems to work, judging by the output variable $errmsg being "Success", but the filehandle in the code is still zero, thus the SMTP transaction never takes place.

Does anyone have any idea if there could be something wrong with SMTP, or perhaps with permissions on the fsockopen function? Is there a PHP configuration variable for fsockopen that I don't know about?

The resolution to this problem is simple:

fsockopen relies on dns or host files to resolve the hosts.

For some reason, against my will, something removed the localhost entry from my /etc/hosts.

Once it was added back in, voila!