[Mailman-Users] big list not posting

[Webmaster]

 hi,
for some reason im having a problem with a big list 50,000 members i tested
out my other lists and they work, whenever i send a message it stalls and
the deliverer script process uses 90% cpu usage so i end up killing that and
the message gets lost for ever,also whenever i go on the members management
page for this list it takes forever and then again that process goes to 90%
cpu usage,do i have to wait longer since its a big list,or does anybody know
whats wrong?postfix is installed bytheway,i check permission and checked
list.dbs all fine.no errors in mail or mailman directory.
version 1.0 (i cant upgrade for some reason thats another story) 312 ram
redhat 6.0 400 mhz
Thank You