Bulk Import Contacts from Thunderbird to Outlook, O365 & OWA

If you are migrating from Thunderbird to Outlook or Office 365, or simply switching to a new device. Importing Thunderbird Address Book contacts from Personal, Remote, or Collected Address Books, that too without any field mapping issues, can be tricky, especially when managing large Address Books.

Export Thunderbird contacts to Outlook 365 or Outlook.com/OWA also enables you to access them easily over the cloud anytime, anywhere, simply with login credentials.

How Mozilla Thunderbird & Microsoft Outlook Manage Contacts?

Mozilla Thunderbird, as an email client, stores its Address Book in its profile folder. Before Thunderbird Version 78, Address Books were stored in .mab format. However, after Version 78, they are stored in .sqlite and .json formats to reduce the chances of corruption.

Microsoft Outlook desktop client stores its contacts in its proprietary format, that is, PST (for Windows) and OLM (for Mac).

Despite this, Thunderbird enables a native direct export of all its Address Book contacts in CSV format, which can be directly imported into Outlook for Mac as well as Windows using the Import/Export option.

Note: Outlook 365 and Office 365 account refers to the same email account with the Microsoft license.

How to Import Contacts from Thunderbird to Outlook? Free Manual Way

In case there are limited contacts, an Address without an extensive field description. Manual approach using CSV import and export is the recommended approach on Mac & Windows desktops.

Keep in Mind: It does require additional technical skills and manual data handling, as there is no bulk export Address in Thunderbird. The manual import also requires a certain level of error handling, as suggested by the user.

1. Open Mozilla Thunderbird.
2. Go to the Address Books section (Alt+2).
3. Right-click each Address Book one by one and press Export.
4. Name & save them in your PC at an easy-to-recognize location.
5. Open Outlook New/Classic.
6. Click on File options on the top left.
7. Click on Open & Export >> Import/Export.
8. Choose “Import from Other Program or File” and press Next.
9. Select the CSV option and browse the file.
10. Press Next and preview what you are importing.
11. Select the suggested destination.
12. Choose the mapping details. Then press Finish.

This will export Thunderbird contacts to Outlook and save them locally, not into any specific account. To transfer them to an Outlook.com or O365 account, set up the account in Outlook and simply drag and drop the contacts.

Export Thunderbird Address Book to Outlook 365 or Outlook.com Account – Using Only Thunderbird

An Outlook.com or Office 365 account can be directly connected to Thunderbird via IMAP. With the simple drag & drop, you can transfer Thunderbird contacts to Outlook.

1. Open Thunderbird.
2. Go to the Navigation menu >> New Account.
3. Select Email.
4. Enter your Office 365 or Outlook.com Email Account and your full name.
5. Log in with Microsoft.
6. Once logged in, go to the Address Book section.
7. Locate the Remote Address Book associated with your Outlook email account.
8. Select contacts from the other Thunderbird Address Book (Personal, Collected, or any custom Address Books). You can bulk select with Shift or Ctrl.
9. Drop them into your Outlook.com or Office 365 Address Book.

Verify a successful import of contacts from Thunderbird to Outlook by logging in to the account in Outlook Web App.

What is the Best Way to Export Thunderbird Address Book to Outlook?

Here is a table of comparison between the manual approach and the automated tool to transfer Thunderbird contacts to Outlook.

FAQ: Import Contacts from Thunderbird to Outlook

Q1: Why are my contact fields mismatched after import?
With the default field mapping in the manual (Import/Export CSV) approach, contact fields like First Name, Email, Phone Number, etc., may be incorrectly matched. You can use the custom field mapping option in Outlook or use the automated tool.

Q2: Why are some contacts missing after importing Thunderbird Address Book to Outlook?
This is often due to accidental human error or corruption caused during manual contact transfer.

Q3: How to avoid duplicates when importing Thunderbird contacts to Outlook?
At the time of import (CSV, PST, OLM), choose the option to “Replace Duplicates with Items Imported” or “Do Not Import Duplicate Items”.

Q4: Can I directly export Thunderbird contacts to Outlook 365 without CSV?
Yes, you can configure your Office 365 account directly into Thunderbird and use drag and drop to transfer contacts from Thunderbird to Outlook 365, or you can use the recommended automated tool when dealing with large, sensitive mailboxes.

Do you need more help to import contacts from Thunderbird to Outlook?

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