Written by Jennifer Walsh. Reviewed for technical accuracy by Shubham Dixit, Independent Expert in Email Forensics and Data File Conversion.
Shubham is an independent external reviewer and not an employee of PCDOTS.
Quick answer. Migrating Zimbra to another new server comes down to your target and what you carry. For mail, Zimbra speaks IMAP, so imapsync or the destination’s built in migration moves it free to a new Zimbra, Exchange or Office 365. Calendars and contacts move cleanly Zimbra to Zimbra through Zimbra’s own export. Name the target first and the path is short.
On this page
First, where is it going
The phrase “another new server” hides the one decision that shapes everything, what is the destination. A fresh Zimbra box, a Microsoft Exchange server, or Microsoft 365 all pull the mail across in slightly different ways, and by far the most common of these in practice is a move to Office 365.
The good news is that the mail itself travels the same way to any of them. Zimbra speaks IMAP, and so does every one of those targets, so moving the messages is an IMAP job that costs nothing. Where the routes differ is in the extras, the built in migration a destination offers, and whether you also need calendars and contacts to come along. So name the target, then pick the matching path below.
One source, several destinations. The mail travels by IMAP to all of them.
“With Zimbra the mail is the easy half, it is an IMAP server, so imapsync or the target’s own IMAP migration will move every mailbox across for nothing. What people forget is that IMAP only knows about mail, so calendars and contacts do not ride along. If the destination is another Zimbra you are lucky, its own export keeps those together, but moving them into Exchange or 365 is a separate step. The cleanest projects are the ones that decide up front which of the two they actually need.” Shubham Dixit, Email Migration reviewer (draft, pending approval)
The free way for mail, IMAP
Whatever the target, the mail moves over IMAP, and you do not need to buy anything to do it.
imapsync. The free, open source tool imapsync copies mail from one IMAP server to another, so it moves each Zimbra mailbox into its counterpart on the new server. You give it the Zimbra and target hosts and the account credentials, and it syncs the folders across. Both servers need IMAP reachable while it runs.
The destination’s own migration. If you are moving to Office 365 or Exchange, the target has this built in. In the Exchange Admin Center, choose migration, then an IMAP migration, and feed it a CSV of users plus your Zimbra IMAP endpoint. It pulls the mail in as a managed batch, which is the natural choice for many mailboxes at once. For the full Office 365 walkthrough see our guide to migrate Zimbra to Office 365.
Zimbra to a new Zimbra server
If the new server is also Zimbra, you have an easier and more complete option than IMAP, because Zimbra’s own tools carry everything, not just mail.
Per account, a user can export a mailbox to a TGZ file from the Zimbra web client under Preferences, Import / Export, which includes mail, calendars and contacts, then import that TGZ on the new server. For a whole server, the admin tools zmbackup and zmrestore, or the command line zmmailbox, move accounts across in bulk. This route keeps the groupware intact, which plain IMAP cannot.
Calendars and contacts
This is the catch worth planning for. IMAP carries mail only. So a move to Exchange or Office 365 over IMAP brings the messages but leaves calendars, contacts and tasks behind, and you handle those separately, exporting Zimbra calendars as ICS and contacts as CSV or vCard and importing them into the new system.
Only a Zimbra to Zimbra move, through the TGZ export above, keeps mail and groupware together in one step. If your target is not Zimbra, budget a little extra time for the calendars and address books.
The method follows the target. Only a Zimbra to Zimbra move keeps everything together.
When the old server is gone, a tool
The free routes assume the Zimbra server is still live. If it has been decommissioned and you are left with exported TGZ files, or you simply want many accounts pushed to the new server without setting up IMAP on each source, a migration tool reads the Zimbra data directly. The PCDOTS Zimbra Converter loads Zimbra TGZ exports, including orphaned ones with no live server behind them, and sends the mail to the target over IMAP in bulk. Being honest about scope, because it delivers over IMAP it moves mail, the same as the free routes, so its real value is reading the Zimbra store when there is no server left and handling a large batch in one pass. There is a free version that migrates ten items per folder so you can test it first.
The tool route, for orphaned Zimbra exports or a large batch.
Here are the steps with the screens.
Step 1. Install and run the migrator on Windows, then open the menu.
Step 2. Choose Email Servers, select Zimbra, and load your TGZ files.
Step 3. Open the Export menu and select IMAP.
Step 4. Enter the new server login and start the migration.
For specific destinations, see our guides to migrate Zimbra to Office 365 and move Zimbra emails to MDaemon, and for a comparable server move, migrate Kerio to Exchange Server.
The methods compared
Match the route to your target and whether the old server is still running.
| Method | Best for | Good to know |
|---|---|---|
| imapsync or built-in IMAP migration | Mail to any target, free | Mail only, both servers live |
| Zimbra export or backup | Zimbra to Zimbra, free | Keeps calendars and contacts |
| Zimbra Converter tool | Orphaned TGZ or a big batch | Reads TGZ, mail over IMAP |
Frequently asked questions
How do I migrate Zimbra to a new server for free?
For mail, use imapsync to copy each mailbox over IMAP, or use the destination’s built in IMAP migration if you are moving to Exchange or Office 365. Both are free.
How do I migrate Zimbra to Office 365?
Office 365 has a built in IMAP migration, feed it a CSV of users and your Zimbra IMAP endpoint. It moves the mail, and calendars and contacts are handled separately. Our dedicated guide covers it in full.
Will my calendars and contacts move too?
Over IMAP, no, that carries mail only. A Zimbra to Zimbra move through the TGZ export keeps them together. For Exchange or 365 you export calendars as ICS and contacts as CSV or vCard separately.
How do I migrate if the old Zimbra server is gone?
Use a tool that reads the exported Zimbra TGZ files directly and pushes the mail to the new server. That works without a live Zimbra server, which the free IMAP routes require.
Can I move many accounts at once?
Yes. A destination’s IMAP migration takes a CSV of users for a batch, Zimbra’s zmbackup handles a whole server, and a migration tool processes many TGZ files in one pass.
Is a Zimbra to Zimbra move different?
Yes, and easier. Zimbra’s own export and backup tools carry mail, calendars and contacts together, so you do not need IMAP or a separate groupware step.
Start by naming the destination
Do that one thing and the rest falls into place. If it is another Zimbra, use Zimbra’s own export or backup and everything travels together. If it is Exchange or, as it usually is, Office 365, move the mail free over IMAP with imapsync or the destination’s own migration, then bring the calendars and contacts across separately, and lean on the dedicated Office 365 guide for the details. Keep a converter in reserve for orphaned TGZ files or a large batch. Decide where it is going, and migrating Zimbra to a new server stops being a mystery.
