[horde] Allow only my domain mails

[Chuck Hagenbuch]

Quoting Antu David Raj <antu at npgco.com>:

>  My Horde system sending lot of spam with different domain id, I check the
> system the message id comes from horde only. Is that any possibility to
> allow only my domain to sending mail out?

People can fake email from more or less anyone, so it is very unlikely  
that this has anything to do with your Horde install. If you have  
direct evidence otherwise we can certainly look in to that, but  
otherwise, your only options are to look into things like SPF.

-chuck