I have ONE GWIA, POA, MTA and multiple domain names. Now, the need is:

for couple of specific users we need to have additional domain names from which they can correspond.

For ex:

1. ONLY user1@abc.com also needs to get emails for user1@xyz.com not other users. Return-reply can be from preferred domain name

2. but if the need changes to have return-reply as xyz.com then what - create secondary domain and postoffice with another GWIA in the same box?

Please help.