How to Easily Convert OLM to Thunderbird with Attachments?

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Updated on
October 17, 2025

7 minutes Read

User Query: ”I have been working with Outlook for Mac for a long time. I have most of my important emails saved in OLM format. Now I want to switch to Thunderbird because it is free and a lot easier to use. So, can anyone explain how I can transfer my OLM files to Thunderbird?

Summary: Outlook is a popular email client application among Mac users for managing emails, contacts, calendars, etc. But some Mac users prefer to switch to Thunderbird because it is open source, lightweight, and platform-independent. So, do you also have the same query and want to convert OLM to Thunderbird without losing any data or attachments? You’re on the right track. In this blog, we will discuss the manual method and a professional MacSonik OLM Converter Tool for conversion. These methods are verified and trusted by many IT professionals for a fast and 100 percent accurate migration..

Mac Outlook vs Thunderbird

Microsoft’s Outlook for Mac is a feature-rich email client that stores all mailbox information in the OLM file format. It is great for professionals, but Outlook is only available for macOS and is a subscription service through Microsoft 365. Thunderbird is a free, open-source email client created by Mozilla. Thunderbird is free, multi-platform, and stores emails in MBOX format, making it easily manageable and flexible.

Simple Steps to Convert OLM to Thunderbird

  1. First, open the OLM Converter tool on your system.
  2. After that, click Select files to select and open your OLM files and click Next.
  3. Then, select your required OLM files to be migrated from the folder hierarchy, preview them, and click Next.
  4. Further, select Thunderbird as the saving format from the listed File Formats.
  5. Finally, apply advanced filters and click Convert to start the migration process.

Need to Import OLM files to Thunderbird

There are various reasons motivating users to switch from Outlook for Mac to Thunderbird:

  • Thunderbird is a free open-source email client, and Outlook requires a license.
  • Thunderbird supports cross-platform usage on Windows, macOS, and Linux.
  • Also, Thunderbird uses the MBOX file format, which is easy to back up and manage.
  • There is no dependency on Microsoft 365 or Exchange.
  • It gives users more control and customization options for their mailboxes.

Preparations before conversions

Before starting the process to export your OLM files to Thunderbird, make sure to complete the following requirements.

  • Have a backup of your existing OLM files just in case.
  • Have Thunderbird downloaded and installed on your system.
  • When performing the migration, close all email client applications running in the background.
  • If you are importing directly to Thunderbird, ensure you have an internet connection.
  • If migrating directly to an email profile, note your account information.

Free Manual Method to Export OLM to Thunderbird

Thunderbird does not support direct import of OLM files, but we can use an alternative indirect method for migration. The IMAP account will act as a bridge between Outlook for Mac and Thunderbird for syncing emails. The process is as follows:

Step 1: Set Up the IMAP Account in Outlook for Mac

  1. First, open Outlook for Mac and select Tools > Accounts.
  2. Then, click on the plus (+) button and select New Account, and enter your Gmail address and password.
  3. Once your account has been connected, Outlook will start syncing with your Gmail account.

Step 2: Move OLM Emails to the IMAP Account

  1. In Outlook for Mac, select the emails or folders you would like to migrate.
  2. After that, drag and drop them into your new Gmail (IMAP) folder and wait for the sync.
  3. Now you have migrated all your OLM emails to your Gmail account using IMAP.

Step 3: Set Up the Same IMAP Account in Thunderbird

  1. Now, open Mozilla Thunderbird on your computer.
  2. Then select Menu > Account Settings > Add Mail Account.
  3. And, put the same Gmail information in that was used before.
  4. At last, Thunderbird will sync the emails that are in the Gmail account automatically.

Once the sync is complete, the OLM emails should be in Thunderbird.

Drawbacks of a Manual Method

Although this method is free, there are some drawbacks:

  • Large mailboxes take a long time to sync.
  • Attachments don’t always sync properly.
  • It requires an IMAP mailbox and Outlook for Mac.
  • Not recommended for non-technical users.
  • If syncing fails, you risk losing data.

Specialized Method to Convert OLM to Thunderbird

The specialized OLM Converter tool is an efficient tool to convert your required OLM files to Thunderbird. The tool can easily provide users with solutions to the problems faced in the manual method. It handles bulk conversion of OLM files easily without any data loss. Additionally, it offers various advanced features to users, such as duplicate remover, date filters, including attachments or not, and more. Also, the tool focuses on the authenticity of conversion and keeps user data safe. Moreover, the software has strong data privacy standards, which keep user data safe and do not store any important data. Users can also convert OLM files to HTML and other file formats using the converter tool.

One-Time Service Option:

If you prefer not to deal with software installation and technical steps. You can request a one-time OLM to Thunderbird migration service from our support team. Our experts will perform the OLM email transfer securely to Thunderbird on your behalf, fast, safe, and cost-effective.

Benefits to Choose the OLM Converter Tool

  • Migrate from OLM to Thunderbird and additional formats, including MBOX, PST, EML, and more.
  • Transfers all attachments, maintaining email structure and formatting.
  • Special features include removing duplicate emails, a date range filter, and a preview option.
  • Free demo available to test prior to making a purchase.
  • Compatible with all versions of macOS and Windows.

Professional Way to Convert OLM to Thunderbird

  1. Initially, install and launch the converter tool on your system.
  2. After that, click Select Files to select and open your OLM files, then click Next.
  3. Now, from the tree structure, choose your desired emails, preview, and click Next.
  4. Moving on, choose Thunderbird from the listed file formats, and apply advanced filters.
  5. Finally, click Convert to start the conversion.

Real-Life Scenario:

Amilia, a graphic designer, has been using Outlook for Mac to handle her client communications. However, she recently decided to migrate to Thunderbird because it’s easy to customize and it does not cost anything. She decided to use the manual method for converting her OLM data; however, it didn’t go as planned. Then, she tried the proficient OLM Converter Tool to efficiently transfer OLM Files to Thunderbird. The tool completed the entire migration within a few minutes, while keeping all attachments, folder structure, and email formatting intact.

Conclusion

To sum up, this blog is a complete solution for users looking to convert OLM to Thunderbird. We have discussed manual as well as professional methods for an efficient conversion. Users can perform any conversion method that suits them best as per their requirements. However, for users looking to migrate OLM files in bulk, we strongly recommend using the proficient OLM Converter Tool. The proficient converter allows users to bulk migrate their files without losing any data, and keeps data safe.

Frequently Asked Questions

Q1. How can I import an OLM file into Thunderbird?

Ans. You can manually import OLM files into Thunderbird by using an IMAP-based method. First, add an IMAP email account in Outlook for Mac to sync your emails. After that, add the same IMAP account in Thunderbird, and your emails will appear there automatically. However, it can be time-consuming for bulk migration. Therefore, you can use the professional converter tool for bulk migration.

Q2. Is it possible to convert OLM to Thunderbird in bulk?

Ans. Yes, the OLM Converter Tool supports batch conversion. You can add multiple OLM files or an entire folder at once and transfer them all to Thunderbird in a single go. This saves time and ensures that none of your emails or attachments are missed during the conversion process.

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