[exim] exim ejects email from hostname with "_"

Hi,

We installed Exim 4.43 on FC2. It is faster than sendmail, which is
great. However, sending email from a host named "canon_bw" was always
ejected. Then we changed the hostname to canonbw. It works fine. Is this
the way exim works or an option we can configure?

Thanks.

--
Regards,

Steve Zeng
Systems Administrator
Mainframe Entertainment Inc
T: (604) 628-1000 ext 5293