Individuals and businesses that want a web-based collaboration platform might want to switch from Microsoft Outlook to Zimbra. One common problem during this change, though, is getting to old Outlook OST emails in Zimbra.
When Outlook is connected to Exchange, Microsoft 365, or IMAP accounts, it makes offline storage files called OST files. You can't import these files directly into Zimbra because they depend on profiles. Zimbra can restore mailboxes from backups in the TGZ (Tar GZipped) format, so OST data needs to be converted into a format that works with it.
In this guide, you will understand:
OST files are not mailbox files that can be moved around. They are copies of server data that stay linked to the Outlook profile where they were made.
On the other hand, Zimbra works with:
Because of this difference in structure, you can't upload or restore an OST file directly into Zimbra. First, you need to convert the OST data into TGZ format so that it can be used.
Zimbra uses the TGZ format to store full backups of mailboxes in a compressed archive. It could include:
When you restore data in Zimbra, TGZ files are recognized and brought in using the Zimbra import/conversion feature.
So, converting OST to TGZ makes the move organized and works with everything.
You can't directly import OST into Zimbra by hand. But if you can get to Outlook, you can use an indirect method.
This method won't work if the OST file is no longer linked to the original profile.
When manual synchronization isn't possible, the best way to go about it is to convert the OST file into TGZ format.
The ToolsGround OST to TGZ Converter can read offline OST files and convert mailbox data to TGZ format. You can then import this data directly into Zimbra.
Steps to Convert OST to TGZ
Step 1: Install the converter on your computer and open it.
Step 2: Manually add the OST file.
Step 3: Let the program look through and show you the mailbox folders.
Step 4: Choose the folders you need or the whole mailbox.
Step 5: Pick TGZ as the format for the output.
Step 6: Begin the process of conversion.
When the conversion is done, you can use the import feature in Zimbra to bring in the TGZ file that was created.
After the conversion:
Zimbra will restore the mailbox data in the right way.
1. Can Zimbra open an OST file directly?
No, Zimbra does not support the OST format. Before you can import the file, you need to convert it into a format that works with it, like TGZ.
2. What happens if my OST file is orphaned?
Outlook won't let you open an orphaned OST file. In these situations, direct IMAP sync isn't possible, so you have to convert OST to TGZ.
3. Is TGZ the only format supported by Zimbra for import?
Zimbra mostly works with the TGZ format for importing complete mailboxes and restoring backups.
4. Will attachments and folder structure be preserved during conversion?
When converted correctly, the TGZ file keeps attachments, folder structure, and metadata.
5. Can the ToolsGround OST to TGZ Converter work without Outlook installed?
Some conversion tools can work with OST files on their own, which can be helpful if you can't get to Outlook.
To move Outlook OST emails to Zimbra, the formats must be compatible. Converting OST files to TGZ format makes sure that the migration goes smoothly and in a structured way, since OST files are not directly supported.
Manual IMAP synchronization only works in certain situations, and it needs to have Outlook open. A good way to convert orphaned or large OST files makes the process easier and ensures that mailbox data stays safe during the move.
