Prevent mails being sent in with fake local from name

[iprigger]

Hi All,

Once in a while spammers try to send in mails with one of the local mail addresses without authentication - is there a way to prevent this?

i.e. someone just sends in the mail with i.e. test@localdomain.com using plain smtp commands from a server hosted somewhere external...

I do have SPF, DMARK & DKIM in place.

Thanks
Tobias