Sendmail problem with Backuppc

Hi all

Not sure if this is the right place to ask this question as it
involves an email problem with Backuppc.

I setup Backuppc on CentOS 4.6. I tried sending test email to myself
with the following command.

su backuppc
/usr/bin/BackupPC_sendEmail -u palm101@domain.com

Then I would get the following output:
Sending test email using /usr/sbin/sendmail -t -f backuppc@domain.com

Now, it seems to be hung for about a minute or 2 before returning the
prompt to me.

Then I see the mail in the mail queue when I execute the command
mailq. The mail seems to be never sent but if I execute the command
sendmail -q -v. I can see that it can actually be sent to the
destination correctly.

Problem is, why is it not sending the mail immediately? I had to run
sendmail -q in a cron job to force it to be sent.

Any idea how to to fix this?