Incorrect "From" address on Order Confirmations

I've used Zen Cart for a few years now. Just set 1.3.8a up on a new site, but getting the following problem. Order Confimations have the following in the from field:

From: [email protected]; on behalf of; MyShop.net [[email protected]]

I have a VPS hosting plan. MyMainSite is the main domain registered on the VPS - I also use my own nameservers which are ns1.MyMainSite.com & ns2.MyMainSite.com. MyShop.net is a totally separate domain which is also running on the VPS. It has its own e-mail accounts etc. i.e. [email protected]. When I look in tools=>server.version info - I have the following information:

Server Host: host.MyMainSite.com (xx.xx.xx.240)

However Zen Cart is installed on MyShop.net (xx.xx.xx.241)

What I would like is for the Order Confirmation emails to simply say; From: [email protected] - Is there anyway I can change this?

You'll need to talk to your hosting company about that, since Zen Cart has no control over sending emails "on behalf of" anyone. It must be something your server is adding for you, presumably to alert recipients to possible spoofing.