Downloading mailbox from replica server

Hi,

I have two IMAP/LMTP Dovecot server in replica (version 2.3.4.1) both connected through an IPsec tunnel, I use LDAP/AD for /userdb, /all seems to be working.

I have a question: if I switch my Thunderbird/Outlook client to use the other server I have to download again all the emails, about 10 GB.

Is there any way to avoid this? Do I have to download again all the folders every time I switch from node A to node B on my client?

Thanks!

Regards