RE: [exim] Exim rejects: syntactically invalid argument

Herb Martin wrote:

> I can imagine creating a custom ACL Deny stanza
> that implements this while whitelisting some sources,
> but is there a trivial way to do this in exim?

You could use helo_accept_junk_hosts (and disable helo_allow_chars),
though this disables all syntax checks for HELO/EHLO.