I don't know its DNS or Apache Prob!

[system at eluminoustechnologies.com]

Hello All,

I have a domain name abc.com the named database is also perfect with all
cname NS MX and A records.
whenever i type mail.abc.com It gets Redirected to home page of someother
domain xyz.com(The home page is of xyz.com but the url remains
mail.abc.com) which is also hosted on the same server where abc.com is.
and its happening to all the domains that are hosted on the server. every
mail.alldomain.com goes to the home page of the xyz.com.
Now When I add a ServerAlias to abc.com as mail.abc.com in my httpd.conf it
works Prefectly.but i have around 1000+ Websites hosted on the server and
every mail.Anything.com goes to the home page of xyz.com whereas it should
go to the Apache's Default Page or the Home Page of its own site.but that's
not happening

I am so confused what has to done.

Rgds,

Tina