We have a system running CentOS 5 with Plesk 8.6 and Qmail running. Our primary domain is hosted through Media Temple. When Plesk and Qmail are hosted on a single Dedicated Virtual server, it reads the primary server IP and domain and reports that when sending emails from the system.

Our pages are written in PHP so we are using the mail() function. While our email goes out to everybody, several enterprise email domains reject our email because it shows a different originating IP (our primary server IP and domain) than the domain we list in the 'from' address. This is not modifiable. Every domain we own of course does have its own IP as well underneath our primary server IP.

I have seen several places online that provide a patch, specifically - which allows Domain Binding:

"DomainBindings -- For servers that host multiple domains or have multiple IP addresses assigned to them, it is sometimes useful (or important) to have qmail use a specific IP address for its outgoing mail. By default, qmail uses whatever address the OS chooses for all outbound connections. With this patch, you can specify which address to use. It uses a control file similar to smtproutes to specify the outbound IP address to use, based on the sender's domain (local copy) (pyropus.ca)"

Qmail Link

First off I do not have netqmail installed so I'll need to find another source, but also I am completely unfamiliar with applying patches to qmail. Will I lose email services if I patch? Is it a simple apply and use process? Will my existing email accounts and data be restored after the patch?

I am very, very new to unix/linux so this does make me a bit nervous but I am the only person who can make the change and it is one our company "HAS" to have. Any ideas?