I'm using exim on both the sending and relay hosts, the sending host seems to offer:
HELO foo_bar.example.com
Response:
501 Syntactically invalid HELO argument(s)
I'm using exim on both the sending and relay hosts, the sending host seems to offer:
HELO foo_bar.example.com
Response:
501 Syntactically invalid HELO argument(s)
grep, although I'm not good enough to come up with the proper re, anyone else?
Possibly a problem with underscores in the hostname? http://www.exim.org/lurker/message/20041124.113314.c44c83b2.en.html
Underscores aren't actually valid in internet host names, despite some people using them anyway. A sane DNS server should not allow you to have records for them.
Change your system's host name so it's valid, hopefully this will fix it.
The argument to HELO
should be a hostname or an IP address. foo_bar.example.com is neither an IP address nor a hostname (underscores are illegal in hostnames), so the error message is correct and there is nothing to fix.