Server name in From field in email

In the email itself which arrives in inbox, instead of having the sender's email as the From address, I get this:

@my-mail-server-address.com

That is, the sites admin's email (within < >) AT the name of the server.

I have found an issue regarding another module (htmlmail.module) which had the same problem: #382950: Causes server e-mail "From" address
However, it seems that forward module is not suffering from this problem because in line 851 there is the "fixed" command:

$message['headers']['Content-Type'] = 'text/html; charset=utf-8';

Could anyone confirm or help? Thanks!