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. Moving Zimbra to Office 365 depends on what you have. For a live Zimbra server, Microsoft 365 has a built in IMAP migration in the admin center that pulls mailboxes across for free. For Zimbra TGZ export files, a converter reads them and uploads the mail into 365. Both keep your folders and attachments.
On this page
Start here, a live server or TGZ files
The right way to move Zimbra to Office 365 depends on one thing before anything else, whether the Zimbra server is still running. If it is live and you have admin access, Microsoft 365 can pull the mailboxes across itself, for free, over IMAP. If all you have are TGZ export files, or you cannot touch the server, a converter reads those files and uploads the mail into 365. So the first question is not which tool, it is what you are holding, a running server or a folder of TGZ files.
A running server goes through IMAP migration. TGZ files go through a converter.
Which way fits you?
For a live server with admin access, the built in IMAP migration in the Microsoft 365 admin center moves the mailboxes for free and suits a whole team at once. For TGZ files, or when you only have one user or no admin rights, a converter reads the export and uploads it, and it can also carry contacts and calendars that IMAP migration leaves behind. Here is how they compare.
IMAP migration for a live server and a whole team, a converter for TGZ files and richer data.
Migrate a live Zimbra server free with IMAP migration
If the Zimbra server is running and you are an administrator, Microsoft 365 can migrate the mailboxes itself, at no extra cost, using its built in IMAP migration. This is the route the old guides missed.
Step 1. In the Microsoft 365 admin center, open the Exchange admin center, then Migration, and start a new IMAP migration.
Step 2. Create the 365 user mailboxes first, then prepare a CSV listing each mailbox and its Zimbra sign in details.
Step 3. Enter the Zimbra IMAP server address and port, upload the CSV, and let Microsoft connect.
Step 4. Start the batch. Microsoft pulls the email across in the background and keeps the folder structure.
It is free and handles many users at once, which makes it ideal for a company move. The catch is that IMAP migration carries email and folders only, not contacts or calendars, and it needs admin access to both sides. If that does not fit, the converter below works from TGZ files instead.
Migrate Zimbra TGZ files to 365 with a converter
When you have Zimbra TGZ exports rather than a live server, or you are moving a single account without admin rights, a converter reads the TGZ and uploads it straight into Microsoft 365. The PCDOTS Zimbra Converter loads one or many TGZ files, connects to your 365 account, and transfers the mail in one run while keeping folders and attachments in place, and it can bring contacts and calendars across too. A free demo moves a limited number of items per folder so you can test it first, and the full version lifts the limit.
Reading Zimbra TGZ files and uploading them straight into a Microsoft 365 mailbox.
Here are the steps with the screens.
Step 1. Run the converter on your Windows PC and open the menu.
Step 2. Choose Email Servers, then load your Zimbra TGZ files or folder.
Step 3. Preview the data, then open Export and choose Office 365 as the destination.
Step 4. Enter your Office 365 login, click Save, and the upload runs on screen.
“The honest split is simple. A live Zimbra server with admin access should go through Microsoft’s own IMAP migration, since it is free and built for many mailboxes. The moment you are working from TGZ exports, or you need contacts and calendars and not just mail, that native path runs out and a converter that reads the TGZ is the right tool. Match the method to what you actually hold.” Shubham Dixit, Email Migration reviewer (draft, pending approval)
Keeping folders, contacts and attachments
Whichever route you take, the goal is a 365 mailbox that mirrors the old Zimbra one. Both methods keep the folder tree so Inbox, Sent and custom folders stay separate, and both keep attachments inside their messages. The difference is reach. IMAP migration moves email and folders, while a TGZ converter can also bring contacts and calendar entries that live in the export. If your plan is to land the data as a file first, you can also convert the mail to PST and then import that PST to Office 365, and the same tool can handle other sources like OLM.
The two methods compared
When the free native route is enough, and when a converter is the better call.
| Method | Best for | Good to know |
|---|---|---|
| IMAP migration | Live server, whole team, admin | Free, email and folders only |
| Zimbra Converter | TGZ files, single user, no admin | Free demo, adds contacts and calendars |
| Doing nothing | Not an option, data stays stuck | Zimbra and 365 do not talk directly |
Frequently asked questions
How do I migrate Zimbra to Office 365?
For a live Zimbra server with admin access, use the free IMAP migration in the Microsoft 365 admin center. For Zimbra TGZ export files, use a converter that reads the TGZ and uploads the mail into 365.
Is there a free way to move Zimbra to Office 365?
Yes. Microsoft 365 includes a built in IMAP migration that pulls a live Zimbra server’s mailboxes across at no extra cost, though it moves email and folders only.
How do I migrate Zimbra TGZ files to 365?
A converter loads the TGZ exports, connects to your Office 365 account, and uploads the mail in one run, keeping folders and attachments and adding contacts and calendars.
Does IMAP migration move contacts and calendars?
No. Microsoft’s IMAP migration carries email and folders only. To bring contacts and calendars from Zimbra, use a TGZ converter instead.
Do I need admin access to migrate Zimbra to 365?
For IMAP migration, yes, on both sides. A TGZ converter needs only the export files and the target 365 login, so it works without server admin rights.
Will the folder structure be kept?
Yes. Both routes preserve the folder tree, so Inbox, Sent and custom folders arrive in Office 365 separately rather than merged.
Your Zimbra mail, moved into Microsoft 365
Migrating Zimbra to Office 365 is really a choice between two clean routes, decided by what you have in hand. A live server with admin access belongs on Microsoft’s own free IMAP migration, built to move a whole team at once. TGZ export files, a single user, or a need to carry contacts and calendars point to a converter that reads the TGZ and uploads it. Match the method to your situation, and the Zimbra mail lands in 365 with its folders and attachments intact.
