Sendmail is deferring mail

[Sandeep Gupta]

I'm running Redhat Linux 7.2 and sendmail 8.11.6.

I'm sending mail via python 2.2's smtplib library.  After the python
application is complete, I did a "mailq" and got the following:

====================================================
[/etc/mail][1050]$ mailq
                /var/spool/mqueue (1 request)
----Q-ID---- --Size-- -----Q-Time-----
------------Sender/Recipient------------
g9AMFCw02972*      61 Thu Oct 10 17:15 <sandeep at XXX.com>
                 (host map: lookup (YYY.com): deferred)
                                       <sandeep at YYY.com>
                                       <lawrence at YYY.com>
====================================================

>From what I've seen, the mail will stay deferred indefinitely.
If I restart sendmail with "/etc/init.d/sendmail restart", then the
mail is sent immediately upon restart.
If I specify the command "sendmail -d8.20 -v -q", then the mail is
also send immediately.

Any ideas about why my mail is being deferred?

Thanks