IMAP Sync Issues after Zimbra to Carbonio Migration - New emails not visible in clients (UID discrepancy?)

Hello everyone,

I recently migrated 114 mailboxes from a legacy Zimbra server to Carbonio (Zextras). While the migration seemed successful and all emails are visible in the Carbonio Webmail, we are facing a critical issue with IMAP clients (Thunderbird, K9 Mail).

The Problem: IMAP clients only see/sync emails up to the migration date. Any new emails arriving after the migration are visible in Webmail but are NOT fetched by IMAP clients.

Environment:

• Carbonio CE (latest)

• Clients: Thunderbird on Windows Server 2016 (Terminal Server), K9 Mail on Android.

• Migration path: Zimbra TGZ export/import.

What we have tried so far:

1. Reindexing: Ran zmprov reIndexMailbox user@domain.com start. No change for IMAP clients.

2. Manual UID Bump: If we create a temporary folder, move messages there and then back to Inbox, the IMAP client "wakes up" and sees the messages because they received new UIDs.

3. New Profile: Creating a completely new IMAP profile in K9 Mail still shows only old messages (pre-migration).

Observation: It seems that the UIDNEXT or MODSEQ values are somehow inconsistent or the IMAP index is corrupted in a way that doesn't trigger a sync for new items.

My Question: Is there a more efficient way to "reset" or "restart" the IMAP UID sequence (UIDVALIDITY/UIDNEXT) for a mailbox or a specific folder without manually moving thousands of messages back and forth? With 114 users and some mailboxes having 70k+ messages, the manual "move" method is extremely slow.

Is there any CLI command or database script to force a regeneration of the IMAP index/UIDs for a given account?

Thank you for any advice!