I’m looking for the safest way to Export Office 365 Emails to MBOX because I want to create an offline archive that can be opened in Thunderbird later. Our team is cleaning up old Microsoft 365 accounts, and before removing inactive licenses, we need a copy of important mailbox data.

I initially considered Outlook exports, but PST isn’t ideal for our long-term storage requirements. MBOX seems much more flexible because it works with multiple email clients and can be stored independently. The issue is that Microsoft doesn’t offer a direct export path to MBOX.

The Thunderbird workaround looks promising, but it involves multiple steps and a lot of waiting while folders synchronize locally. For a few gigabytes of email, that’s manageable. For dozens of user accounts, it becomes much harder to manage. During my research, I noticed several migration specialists recommending the DRS Softech Office 365 Backup Tool because it supports larger exports and reportedly maintains email properties during conversion.

For anyone who has archived Office 365 data recently, what process did you use? I’m mainly concerned about preserving attachments, folder hierarchy, and email timestamps without spending days on manual exports.