Advise needed for new mail server

[Mufit Eribol]

Hello,

I have been successfully using postfix+cyrus-imapd (2.4.17) for our 
small company for years on our local server. The emails are now 
accounting to a size of  some 160GB. As we are having power and internet 
problems quite often, I rented a VPS from a world renowned hosting 
company and installed postfix+cyrus-imapd there.

My question is, as I have limited hard disk space (40GB) on VPS, I can't 
(and don't want to) copy all of my local emails to the VPS. The new mail 
server will have a fresh start. But old emails needs to be accessible on 
the local server as well.

Currently, I am planning to change the names of local domains to some 
non-existent name just for the internal lookup (example.com --> 
example2.com), so that we can setup example2.com on our email clients on 
lan. The real domain example.com will be setup on our desktop email 
clients as usual. I think, using example2.com on local lan just for 
reading mails by cyrus will work, but it is not an elegant solution.

I would appreciate any ideas.

Regards,
Mufit Eribol