Major Description
I am proposing 128 character limit for username, and unlimited characters for password.
Our recommendation in docs can be "userid length can be 128 characters, but we recommend that userids don't exceed 64 characters"
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I was just checking active directory as well because these users can be LDAP users, and here are the limits there -
https://technet.microsoft.com/library/Bb727137
"Quick answer is 64 characters for display names and 104 characters for user logon names, however Microsoft recommends that user logon names be kept to 64 characters as well."
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