How to setup email accounts on dedicated mailserver?

[jolly]

We have multiple domains and subdomains hosted on different servers. How can we setup email accounts on dedicated mailserver.
How do we use our dedicated mailserver as primary server and others servers as backup so that if anytime mailserver goes down we dont miss any email.
How to configure MX and other details.
TKs

[Alex[nl]]

I have no answer to your questions but I assume adding the operating system of the server aswell as the e-mail software you're running would help people answer your questions.

If you know which e-mail software you use you could aslo try their webpage to see if they have an online manual.

[jolly]

OS=Red hat 7.2 , sendmail.
But now we are setting up qmail server. We just want this to be mailserver not for hosting sites.

[keyweb]

I assume that you are running this on a separate server from your qmail.
Several things that you need:
1. /etc/mail/local-host-names -- needs to contain the domain names which you will be servicing (the mx record should point to the server.) One domain name per line.
2. /etc/mail/virtusertable -- routes an email address from any particular domain to a mailbox (or to another email address.) One name per line, the email address separated by whitespace (I prefer tab.) If the entire domain is to go to one mailbox then you can use an @domainname mailbox
For example, in local host names you have a domain
mydomain.com

Then in virtusertable you can have
bob@mydomain.com bob
liz@mydomain.com liz
@mydomain.com jack

The accounts bob, liz, and jack must exist on the system. Mail to bob or liz goes to their respective mailboxes for popping, while any other mail to that domain goes to jack.

You can forward to another address by
jill@mydomain.com jill@hotmail.com

If you wish to forward an entire domain to another mail server without messing with each alias you can use (anotherdomain.com is in local-host-names, and thedoamain.com is a valid mail server)
@anotherdomain.com %1@thedoman.com

Since you are using the Redhat rpm to build the sendmail, MAKE SURE that you patch sendmail because of the recent sendmail exploit!

Hope that helps, I am hosting about 400 domain names, so have learned a lot from the school of hard knocks!