at first u need to say your domain where your server is as example we have
the internet IP 11.22.33.44
and we have registered the domain test.com
so at IP a = 11.22.33.44
at the mx = mail.test.com
so now u need to say your email server (mercury) that he have to listen at test.com
u can find it under
mercury core modul configuration
then local domains
here u need add new domain
local host or server = server
internet name = test.com
now u need to know which want to use this domain ?!
configuration - manage local user
then add your user
now u can receive ur emails if u want send it too with this server
u need to configurate your smtp
configuration - smtp server - connection control
add restricton 127.0.0.1 allow
set authenticated smtp con..... ok
set only authent......... ok
then give a name by
auth password file and edit
add the same user with same password
now ur server can receive and send emails (if ur firewall nothing block !?)
if u want more information pls use google it exsist so much manuals for it