In SharePoint 2016 the User information list in sites is not updated from the UserProfiles. The sync job is not working the right way. Probably a bug in SharePoint.
In the user information list or table you can see wrong email addresses and when you share a document with that person in the site you get a bounced email back.
Workaround: trigger an update by giving a user temp. permission on the site or use powershell: Set-SPUser -SyncFromAD You can schedule this for every user on every site. I can share this script when you need it.
See also this discussion on TechNet: