Is the primary identifier of an Active Directory user the 'logonname' attribute?

Question

For security purposes, is the primary identifier of an Active Directory user the 'logonname' attribute?

For example a user with the logonname "bob" is first created then removed from AD, then an another user is created again with the logonname "bob" - is this new user, from a security perspective, equivalent?

The reason I ask this question is due to some recent peculiarities with opening a PST mailfile - as the above example, a user has been removed then recreated with the same loginname, this new user is not permitted to open the previous users pst file despite sharing the same username.

Thanks.

Answer 1

No, the objectSid (a SID) is the primary ID when it comes to assigning permissions. A new user with the same name will have a different objectSid, and therefore will not be able to access files which the original user had permission to.