Email Server Issue

Hi everyone, im running Suse10.3 and its an email server too, running Postfix, Squirrel mail, & dovecot.
***My Scebario ***

the company i work for was recently taken over by another company and they have suggested we carry out an integration in the IT systems, for starters they need us to change a couple of things on the mail server.
they want us to change all our email addresses to have the new company name domain. for example, our current email addresses are

, but they want that to change to for example

The most confusing thing here is, the users here are not to be affected in anyway, they will send mail as usual only that it will have a different domain name at the recipient’s side, and when the reply is sent, its supposed to come through our old domain.
It somehow doesn’t make sense, but is there a way to go about it?
any help guys!

On the receiving side, it’s probable that they want the old email addresses to continue to work for a while, maybe indefinitely. That’s no problem, your email server already accepts them. You will be just telling the email server to accept the new domain also. I assume the new domain is really new, so that hasn’t been already assigned to another Nelly in the company taking yours over.

But what do they really want to do for outgoing email? Do they want you to rewrite all the headers of emails to change the domain? The ones in the envelope are easy to change, but the one inside the message could be tricky, there are many places the old addresses could be used, not just the From:, but also Reply-To:, Cc:, Bcc: etc. Then too you have no control over enclosed or attached mail coming in which may contain old addresses. Maybe you can rewrite the obvious places, but you really want to get the users to change their mail program settings. That’s one plus for centralised mail services, people type in terms of human names, and the system tacks on the company domain.

So you need to go back and ask for some clarification and compare against what is feasible.

Thanks so much for the response. im trying as to gather as much info from these guys so as i can find a way to go about it, problem is their response is really taking long.
Will get bak with some more info as soon as i hear from them.