[Dovecot] Possible to split message store location?

[Pierre]

On 24/sep - 14:55, Patrick Westenberg wrote:
> Pierre schrieb:
>> On 23/sep - 08:17, Patrick Westenberg wrote:
>>> You can set a different maildir (or home location) in your userdb which
>>> points to a different mountpoint.
>>
>> Ok, and then how to get back emails when reading from IMAP, when emails
>> are split in different places ?
>
> It works the same way.
> If a maildir is stored in the userdb and queried from the user_query,
> it overrides the mail_location set in your configuration file.

Yes, but I'm thinking about putting mails in different places, for instance:

unread mails are delivered to server1
read mails go to server2
old mails go to server3...

question 1: can we set more than one alternative storage place (cf alternative_storage in dovecot wiki) ?
question 2: can we split deliver, then ?

I read something about replication, but does not feet my needs.
Also, delivering in other places is not a pb, the issue resides in fetching the good emails. May I do it using namespaces ? How ?