5 June 2026, 07:25 PM
I'm currently helping a small organization move away from Microsoft 365, and one of the biggest challenges we're facing is finding a reliable way to Export Office 365 Emails to MBOX format. Most of our employees plan to use Thunderbird going forward, so having mailbox data in MBOX format is important.
Initially, I assumed Microsoft would provide a direct export option, but after researching the process, I discovered that Office 365 mainly supports Outlook-based exports and PST files. Since Thunderbird doesn't use PST natively, that creates an extra layer of work. I started testing the manual method by connecting Office 365 accounts to Thunderbird through IMAP, creating local folders, and moving mailbox data manually. While the process technically works, it becomes increasingly difficult when dealing with larger mailboxes.
One mailbox I tested contained nearly 15,000 emails collected over several years. The synchronization process took hours, and I constantly worried about interrupted connections, incomplete downloads, and missing attachments. Even after the sync finished, I had to manually verify whether every folder had transferred correctly. For businesses that rely on archived emails, invoices, contracts, and customer communications, that's a significant risk.
Another challenge is maintaining the original folder hierarchy. Many users organize their emails into dozens of project folders and client-specific directories. Recreating that structure manually can be time-consuming, especially when multiple accounts are involved. Storage is also a concern because Thunderbird requires enough local space to download and process mailbox contents before exporting them.
While searching through migration forums, technical blogs, and administrator discussions, I noticed that many professionals recommend automated solutions when mailbox sizes become large. One name that repeatedly appeared was the DRS Softech Office 365 Backup Tool. From what I gathered, users prefer it because it can handle multiple mailboxes, preserve attachments, maintain folder structures, and reduce the amount of manual intervention required during the export process.
What I'm really trying to understand is where the tipping point is. For a mailbox with a few hundred emails, the manual Thunderbird approach seems reasonable. But once you start dealing with several gigabytes of email data, shared folders, archived mailboxes, and years of attachments, the process becomes much more complicated.
Has anyone here recently migrated from Office 365 to Thunderbird or another MBOX-supported email client? If so, how did you handle the export process? Did you rely entirely on Thunderbird, use a hybrid approach, or switch to a dedicated migration utility? I'm especially interested in hearing real-world experiences regarding mailbox integrity, attachment preservation, folder hierarchy retention, and overall migration time.
Initially, I assumed Microsoft would provide a direct export option, but after researching the process, I discovered that Office 365 mainly supports Outlook-based exports and PST files. Since Thunderbird doesn't use PST natively, that creates an extra layer of work. I started testing the manual method by connecting Office 365 accounts to Thunderbird through IMAP, creating local folders, and moving mailbox data manually. While the process technically works, it becomes increasingly difficult when dealing with larger mailboxes.
One mailbox I tested contained nearly 15,000 emails collected over several years. The synchronization process took hours, and I constantly worried about interrupted connections, incomplete downloads, and missing attachments. Even after the sync finished, I had to manually verify whether every folder had transferred correctly. For businesses that rely on archived emails, invoices, contracts, and customer communications, that's a significant risk.
Another challenge is maintaining the original folder hierarchy. Many users organize their emails into dozens of project folders and client-specific directories. Recreating that structure manually can be time-consuming, especially when multiple accounts are involved. Storage is also a concern because Thunderbird requires enough local space to download and process mailbox contents before exporting them.
While searching through migration forums, technical blogs, and administrator discussions, I noticed that many professionals recommend automated solutions when mailbox sizes become large. One name that repeatedly appeared was the DRS Softech Office 365 Backup Tool. From what I gathered, users prefer it because it can handle multiple mailboxes, preserve attachments, maintain folder structures, and reduce the amount of manual intervention required during the export process.
What I'm really trying to understand is where the tipping point is. For a mailbox with a few hundred emails, the manual Thunderbird approach seems reasonable. But once you start dealing with several gigabytes of email data, shared folders, archived mailboxes, and years of attachments, the process becomes much more complicated.
Has anyone here recently migrated from Office 365 to Thunderbird or another MBOX-supported email client? If so, how did you handle the export process? Did you rely entirely on Thunderbird, use a hybrid approach, or switch to a dedicated migration utility? I'm especially interested in hearing real-world experiences regarding mailbox integrity, attachment preservation, folder hierarchy retention, and overall migration time.