reply to a virtual domain?

[Chowroc]

There are 2 domains: zouben.org and dm04.com, they can resolve names for each other, zouben.org has a MX mail.zouben.org(postfix), but dm04.com has none.

Now I have set dm04.com to be a virtual domain of the SMTP Server, I deliver mails from zouben.org to dm04.com, yes ,the mails can be stored to the mailbox I have assigned.

But I have a question: if someone mail as:
FROM: USER@dm04.com
TO: USER@dm02.org
dm02.org has its own mail server, but how can it kown dm04.org is a virtual domain of zouben.org and it should deliver mail to mail.zouben.org?

After that, I build a truly virtual domain: vdm.com, SMTP Server can also store mail to the right mailbox I assigned, but the same problem .

[Thomas Bianco]

maybe i don't entirely understand goal, but wouldn't you simply create an MX for dm02.org as Mail.zouben.org?

am i missing something?

[Chowroc]

Then I will not be very clear about the purpose of building virtual doamins!

I read the postfix documentation and build the
virtual domains: dm04.com & vdm.com, dm04.com is a actually existed domain but vdm.com is not.

I mean, if USER_dm02@dm02.org get a mail:
FROM: USER_dm04@dm04.com/vdm.com

So he will reply:
TO: USER_dm04@dm04.com/vdm.com

MX of dm02.org is smtp.dm02.org, HOW does it know should mail TO mail.zouben.org rather than elsewhere?

thanks.