sendmail queue growing, host name lookup fails

[Eliot Stock]

I just moved from FC2 to FC3 and I think I have my mail sendmail config

just as it was for FC2. Sendmail receives mail for local delivery just 
fine, but outgoing mail does not send.

I use my ISPs SMTP server as a smart host. In sendmail.mc:


define(`SMART_HOST',`relay.plus.net')


'mailq' shows a bunch of mail not being sent due to host name lookup 
failures:


iACC9XnN003813*    6874 Fri Nov 12 12:14 MAILER-DAEMON
                (Deferred: Name server: relay.plus.net: host name 
lookup fail)
                                        <accounts at realcontacts.com>
iACB9XVo003702     8287 Fri Nov 12 11:12 MAILER-DAEMON
                (Deferred: Name server: relay.plus.net: host name 
lookup fail)
                                        
<gemm.com-at-eliotstock.com at errors.gem


If I run sendmail in test mode to test the name lookups, I get this:

[root home ~]# echo '/mx relay.plus.net.' | sendmail -bt -d8.8
ADDRESS TEST MODE (ruleset 3 NOT automatically invoked)
Enter <ruleset> <address>
> getmxrr(relay.plus.net., droplocalhost=0)
getmxrr: res_search(relay.plus.net.) failed (errno=110, h_errno=2)
getmxrr(relay.plus.net.) returns -1 value(s):


[root home ~]# echo '/map host relay.plus.net.' | sendmail -bt -d8.8
ADDRESS TEST MODE (ruleset 3 NOT automatically invoked)
Enter <ruleset> <address>
> map_lookup: host (relay.plus.net.) dns_getcanonname(relay.plus.net., 
trymx=1)
dns_getcanonname: trying relay.plus.net. (AAAA)
NO: errno=110, h_errno=2
dns_getcanonname: trying relay.plus.net. (A)
YES
dns_getcanonname: relay.plus.net
returns relay.plus.net. (0)


And indeed I can ping relay.plus.net ok, but it has no MX record - not 
sure if that's the problem. Does sendmail need to lookup an MX record 
for the smart host before it sends? This worked on FC2 I think, and my 
ISP's DNS records haven't changed.

Cheers,

Eliot Stock.