Re: [exim] syntactically invalid argument(s) - rejected HELO

Marc Perkel wrote:

> I have a customer who is getting real email from korea (yes - there is
> email that isn't spam) . But - getting this in the logs.
>
> syntactically invalid argument(s)
>
> What does this mean?
>
Does host name in HELO contain underscore? We have one Vietnamese client
who has '_ ' in HELO.
Put
helo_allow_chars = _
in your exim configuration file.