Can I install two mail server on my windows2000 server.

yeah, sure you can, you just need to remember that port 25 can only be used once on any one network card, therefore you would either need to run the servers on different ports, which doesnt make sense because SMTP will always be port 25.

or you can put multiple network cards in the computer and put a mail server on each network card.

I have never tried to assign more than 1 IP address to a network card in windows 2000 but id assume that would be a solution too.

A Windows solution for an SMTP server would be Exchange Server, install Enterprise edition and you can use the one server to handle as many domains as you want and you can delegate the domains administration, be careful cos its expensive...

Actually At this time imail is running on my server but now some of my clients wants to worldclient(mdaemon) . so please suggest me how can I solve this problem.
At this time imail is running on my server on port 8383 and I want to know if I will install the worldclient(mdaemon) on another port 3000 , Will it solve my problem.

I want to say thanks in advance for your valuable advice.

hi, I have an mdaemon server running on one of my old machines, its currently getting upgraded to exchange server, but i cant see why it wouldnt work since you are binding to different ports they will act as two seperate servers.

id try it on a test server first, setup a workstation with the configuration and see if it works.

good luck