[Exim] Underscore in domain is being rejected

I am seeing this:

,----
| 501 <mail@st_agency.com>: malformed address: _agency.com> may not
| follow <mail@st
`----

In my fetchmail log, I telneted to the server and did a test:

,----
| 250 tcob1.net Hello bsod.tcob1.net [192.168.0.2]
| MAIL FROM: <sean@kylemore_pass.com>
| 501 <sean@kylemore_pass.com>: malformed address: _pass.com> may not
| follow <sean@kylemore
| quit
`----

Any suggestions

Sean
- --
  Sean Rima                                http://www.tcob1.net
  Linux User:      231986          Jabber:   tcobone@???
  THE VIEWS EXPRESSED HERE ARE NOT NECESSARILY THOSE OF MY WIFE.