Since the publication of this article, ShareGate Desktop has updated and unified the migration interface. The following screenshots may no longer be accurate, we are working on updating them.
In this blog, I will show you how Sharegate manages unresolved users (users that no longer exist) when migrating files, folders and items to SharePoint or between SharePoint sites.
First, it's important to understand that Sharegate is designed for SharePoint power users, not just for administrators and developers. I don't want to get into every detail, but I will present the big picture. Let's start.
The first time you connect to SharePoint, a new entry is created inside SharePoint, in a special list called User Information List. From that moment, Sharepoint is able to track you. For example, creating a document in SharePoint means that you are the author, and it refers to your SharePoint user.
If you decide to migrate your files, items and folders from one SharePoint version to a more recent one, the new User Information List will be empty since nobody has connected the site yet. If you want to preserve the created and modified metadata (author and editor) while migrating your content, Sharegate will automatically fill the User Information List and link your content to it. So what's the problem? If the user account is disabled in Active Directory (fired employee, retirement, etc.), Sharegate won't be able to add it to the User Information List. Why? Because the resolution mechanism in SharePoint completely ignores disabled users in Active Directory. This means that you will end up losing the authors/editors on some content, and the user doing the migration will be assigned instead.
Option 1 - Re-Enable the User in Active Directory
If maintaining the author and editor is critical even if the user is no longer in your company, you could re-enable the user in Active Directory during the SharePoint migration process. This would allow Sharegate to resolve it correctly. I know it's not a perfect solution, but it works. Sharegate does not require a server installation, so it has very limited access to the SharePoint environment.
Option 2 - Configure the Unresolved User Behavior
In Sharegate, you can configure the fallback value when Sharegate is facing a user that can't be resolved at the destination. So, instead of ending up having the user doing the migration everywhere, you can choose which user can be assigned by default.
In the User and group mappings window, you must assign the default user account beside the 'Unresolved users and groups' mapping. Here's the interface:
I've just presented 2 options on how to manage users, that no longer exist, when migrating from one SharePoint to another. There are probably many other solutions out there, but keep in mind that Sharegate has a very limited access to the SharePoint server, and it makes the best out of it. If you want to deal perfectly with this scenario, you'll end up having to run a server-side software that requires special privileges or even direct access to the SQL Server which can lead to other bad side effects.