Hi,

We installed a new BES express and I want to configure our existing bb phones on this new installation.

What would be the steps to do that considering some of our phones avec also personnal email configurations?

Thanks for your help

Does the new BES also have a new SQL database, or does it share the same SQL database as the first BES?

If it's a new SQL database, then you need to wipe each handheld and then re-activate on the new BES.

It is a new database. New exchange server.

What do I do for phones that has personnal email accounts configured as well as the bew one?

Does a backup and restore from BDM will restore all its configuration and emails?

Honestly, why are you concerned with personal email accounts? Isn't that the user's responsibility?
You should be concerned with getting your devices activated on the new BES. Everything after that should be on the user's shoulders.

Wiping the device will delete the BIS service books.
A backup/restore might work, but it will get messy because you need to make sure you don't restore any service books or data from the previous BES configuration.
The restore will need to be done prior to activating on the new BES.