[exim] immediate delivery

Is there a way to get messages delivered immediately from a specific email
address, we send out over 400 messages once in a while to our customers for
maintenance updates but we get messages such as the one below, and messages
stay in queue until the next run. We'd like to have it deliver immediately
for support and billing @ourdomain.com or possibly for a specific esmpta
login.

2007-10-24 13:16:47 1Ikkmc-00005J-Gu no immediate delivery: more than 20
messages received in one connection

Thanks,
Lance

No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.488 / Virus Database: 269.15.9/1090 - Release Date: 10/24/2007
8:48 AM