Migrating to Exchange Online – 401 Unauthorized Error Fix

This year, I’ve been seeing a lot more people and companies want to move to Microsoft 365 for email and other business cloud services. And for good reason: Microsoft has hit the ball out of the park with many of their cloud-based solutions.

I’ve done a number of these migrations before, but recently, noticed something new during the process while using BitTitan’s MigrationWiz tool. When attempting to run the verification process to make sure the source and destination mailboxes can connect to one another, I was getting an error. One that is all too familiar:

401 Unauthorized

Microsoft has recommended MFA – or, “Multi-Factor Location” – for quite a while now with Office 365. The difference is that it is now enabled by default with new tenants/customers. This is a very good thing for security. But for those trying to migrate email from Exchange server or other email providers to Exchange Online using a third-party tool such as MigrationWiz, it puts a hard stop on the procedure until MFA is temporarily disabled on the Microsoft 365 tenant.

This page from Microsoft Docs provides some additional information on how to disable the recommended security defaults for an Azure/M365/O365 tenant.

Just don’t forget to re-enable it when you’re done with mail migrations.

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