Slow multisend

Multisend message passes very slow: between several seconds and whole minute! Even for 4 users it lasts for 9 seconds. Database is new (openfire was installed today). I use embedded database. And CPU usage while multisending is about 9%. Is it bug or policy against spammers? How can I fix it? I have tried various Miranda varsions.
O/S Windows server 2003 sp2, Openfire 3.9.3 connected to my Active Directory.

(openfire 3.10.x does not working with our cyrillic users)

People suggested me that I have use broadcast plugin. So the next question: how can I add broadcasting JIDs to all users in their lists?