[Mailman-Users] Sendmail

hello, 400 mhz pentium 2 320 ram redhat linux 6.0,ive recently installed mailman,now i had a problem with the memory originally i had 64 ram so i added another 256 in there it would choke with only 64,so i had to bring the open connection option (num_spawns ) down to 1 but it would take forever so what sould the setting be for my profile running sendmail the default was 5 should i put it at 5? i have pretty large mailing lists 20,000 members range. Thanks.