Question : cannot send mail from non-windows host in domain

I've installed a new SBS 2008 server in the domain mydom.com, hostname mail.mydom.local. We have a linux host in the domain. It has a NIC for the local domain (webserver.mydom.local) and one for the Internet (webserver.mydom.com). We also have a router/firewall. Topography:

mail (192.168.0.2) > router (192.168.0.1) > Internet (64.129.x.x)
webserver (192.168.0.3) > router (192.168.0.1) > Internet
webserver (64.129.x.y) > Internet

The webserver has its default gateway set to 64.129.x.z, the gateway specified by the ISP.

webserver's DNS entries are 192.168.0.1 (the router), 66.192.88.2, 66.193.88.3 (the latter two being the ISP's). I've also tried setting the 1st name server to 192.168.0.2 (MAIL). Didn't matter.

The webserver can send mail outside the domain, but not to users @mydom.com. webserver is using sendmail.

This all worked under SBS 2003, so there must be something differnt in SBS 2008.

Answer : cannot send mail from non-windows host in domain

So previously the lunix server was using the SBS server as a smart host, but now it is not?

We know from one of your earlier posts that the firewall has changed, and the same change that was stopping you getting to your webserver, is probably stopping your webserver sending mail to your SBS server. So whoever previously commented "you need to fix the firewall" is still as correct now as they were then.

However to get around this....

If you know how to put the sbs2008 in as a smart smart host back into the sendmail.cf then do that and follow these instructions to allow the linux webserver to relay mail through the sbs 2008.
http://msexchangeteam.com/archive/2006/12/28/432013.aspx
http://blogs.technet.com/b/sbs/archive/2008/09/18/how-to-configure-trusted-smtp-relay-in-exchange-on-sbs-2008.aspx

I would probably set the only DNS server on the webserver (/etc/resolv.conf) to also be the SBS Sever. That way there will be no resolution issues.