SmartList Performance on Linux

Hello everybody, We are running a small list of about 250 users on a Linux System using SmartList as the MailingList server. The OS is Redhat Linux Release 7.0 and the Processor: Pentium III running at 448 MHz with 128 MB RAM. By the way, I have the KDE graphics environment ON all the time. It takes around 5-10 minutes to send a single mail to all the users. The MTA we have is sendmail that comes along with Redhat distribution. Can any one help me improve the performance of the mailing list server? Thanks Prashanth K Gujjeti