[exim] Check for domain in acl_check_notsmtp

Hi,

I don't think what I want to do can be done, but I have to ask :)

I have a rather advanced exim setup that I'm really, really happy with.
Exim is incredibly versatile. Thank you!

The server uses fetchmail and gotmail to receive mail from other
pop3/imap servers and hotmail. This works fine, but I'd like to check
the mails for spam. I do this in the notsmtp acl. This also works fine.
But I don't want to check the mail sent from the box for spam, so I have
a condition that checks for headers added by gotmail and fetchmail. This
works good, but makes it hard to download mail via other apps (if there
should ever be a need).

So I was thinking; if I only check mails with a return path _not_ from a
local_domain I should be safe. But this doesn't really seem possible?
Since there's not much I can check for in the notsmtp acl?

Is my understandings of things correct?

Best regards,
Stian