exim: rejected EHLO, syntactically invalid argument

Written by · in Open Source, Systems

If you email having problem with rejected EHLO or HELO, caused by syntactically invalid argument(s).

  • Possible the hostname contains underscore(_).
  • This is not standard practice, having _ for your domain
  • for example takizo_mail.takizo.com
  • Most of the mail server rejected hostname with underscore.
  • Possibility is a Windows Admin

Error message shows in exim’s log;

2007-01-31 09:13:21 rejected EHLO from [123.123.123.123]: syntactically invalid argument(s): stupid_proxy.windowsadmin.com.my
2007-01-31 09:13:21 rejected HELO from [123.123.123.123]: syntactically invalid argument(s): stupid_proxy.windowsadmin.com.my

Solutions: Add this line in exim configuration main section;

helo_allow_chars = _

Now your exim should be working and receive email from the l33t! hostname. _hell_.lamer.com