Hi @ComputerHabit ,
hard to tell, because this could depend on DNS settings (or how the down level logon name - domain\SamAccountName is resolved) or it could also depend on some NTLM settings (Group Policy or so). This could play a keyy role, especially in bigger envirtonments with multiple domains in the same forest.
This is a very intersting diuscssion on the topic, you might just find a some hints there:
Any difference between DOMAIN\username and username@keyman .local?
https://serverfault.com/questions/371150/any-difference-between-domain-username-and-usernamedomain-local
This one I would also recommend:
User principal name vs SAM account name
https://serverfault.com/questions/928115/user-principal-name-vs-sam-account-name
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Regards
Stoyan Chalakov