RE: [Exim] Syntactically invalid hostname

> I guess that's because of the underscore. Unfortunately, I
> cannot force
> people to change their naming. Is there an option in Exim
> 4.04 to ignore
> those errors and accept the message ?

Why not? I would just leave the config and have the persons with the broken setup fix their end. If mail is hampered, it wont be MY problem.