Contactform 7 vs. Spamfilter


I know Contactform 7 isn't a WPMU Plugin - but maybe I can find some help anyway. We are currently facing a problem that we never had before.

The Mail-Server of a project has a firewall that blocks every mail from which isn't send via this exact server. This is to prevent spam from . The only option is turning of this filter or turning it on - there is no whitelist or anything like that.

The problem is - contactform 7 is exactly doing this - sending a mail to - but not using the mailserver, so that every request from the website currently is blocked.

Maybe somebody had a smiliar problem or a smart idea to solve this?

Thanks in advance!