Setting up BitTitan to migrate mailboxes from O365 to another O365 tenant fails source authentication with the error: "Your migration failed while checking source credentials. The request failed. The remote server returned an error: (401) Unauthorized."

It has been a while since I’ve been involved with Office 365 mail migrations but I was recently contacted by a colleague who was setting up BitTitan’s MigrationWiz for a migration and could not figure out why he was not able to authenticate so I hopped on to help. The search results from Google directed me to various documentation provided by BitTitan but none of them lead me to the right solution. I don’t usually use YouTube for troubleshooting as most of us probably feel it takes too long to watch a video as compared to reading a blog post like this but the following video is where I eventually found the answer:

How to solve BitTitan MigrationWiz Error 401 Unauthorized in 2022
https://www.youtube.com/watch?v=iI35AJrGYiw

This blog post serves to help anyone who might encounter the same problem quickly find the answer.

Problem

You attempt to use the Verify Credentials feature in MigrationWiz after setting up the source and destination tenants but receive the status: Failed (Verification)

Navigating into one of the accounts display the following error message:

Your migration failed while checking source credentials. The request failed. The remote server returned an error: (401) Unauthorized.

Solution

The reason why the environment I was troubleshooting in has this failure is because Microsoft had started disabling basic authentication for Office 365 that affects the EWS service that MigrationWiz relies on (3 minute mark in the video). This can be confusing because if you navigate to Settings > Org Settings > Modern Authentication, you’ll see that it states basic authentication is enabled for various services (including Exchange Web Services). The problem here is that this only applies to the modern Outlook client, which MigrationWiz isn’t.

To remediate this, click on the Help & support button at the bottom right corner of the administration console:

Then type in the following string to search:

diag: enable basic auth in exo

Proceed to click on the Run Tests button:

Assuming basic authentication is disabled, we should be provided with a drop down menu box to select a service to enable:

Select Exchange Web Services (EWS) to enable the MigrationWiz dependent service, then click on Update Settings:

The following message will be displayed:

Run diagnostics
Basic authentication has been re-enabled for the selected protocol.

The Basic authentication blocked applications setting has been updated. You should be able to use Basic authentication with the selected protocol within the next hour.

Proceed to try and verify the credentials in an hour or so and the process should complete successfully.

Hope this helps as it took me a bit of time to figure this out.