==== Required information ====
- iRedMail version: 0.7.3
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Linux/BSD distribution name and version: CentOS 5.6
- Related log if you're reporting an issue:
====

I've not been diligent in following upgrade paths, and I still am running iRedMail 0.7.3 on a CentOS 5.6 server with about 250 domains and about 1000 users.

I need to upgrade to a different server anyway (due to disk space issues) and after reading through all the documentation on upgrading iRedMail, I'm a little confused.

What I want when I am done is to have iRedMail 0.8.7 running on a new CentOS 6.4 server, and to migrate all user accounts to that new server.  Do I need to do all the incremental updates on the old server before migration, so that the two servers are running the same version, or can I just apply the MySQL specific updates relating to table structure before migrating the data? 

Please be very specific in your answers as I am still a relative newcomer to Linux.

Thanks in advance.