On prem AD and Azure conflict - permanently deleted user merged with new user

Hello all.  I have a weird issue with AD Sync and Azure/Entra. Back in 2015 a user was created in the on prem AD and at some point, was sync'd with Azure. That user profile has since been permanently deleted (for years now). A new user with the exact same name has recently been added to AD and sync'd with Entra. The problem is that Entra and the MS365 mailbox seem to have retained some of the previous user's information. Specifically, Entra shows a created date from 2015 and Exchange shows the previous user's email address as hidden from the GAL (the later issue being the primary concern). I have verified the new user account has the AD attributes of "false" for msExchHideFromAddressLists and that is has a Nickname. All the proxy addresses are as they should be for the new user. When in the MS365 admin portal for the new user>mail and refreshing the user information I can see that the Show in Global Address List property briefly changes to Yes (while it is refreshing) but then reverts to No. For the life of me I cannot figure out how fix this. Any suggestions?  Thanks.

Edited by jfindley, 08 December 2023 - 01:05 PM.

I would take this up with Microsoft because there is likely no one here that could fix this issue.  I would assume that you have support from Microsoft?

I do have Microsoft support...though admittedly, I usually make that a last resort.

THey should always be the first line of support for any corporate related issues such as this.

You say the user has the same name -- I'm assuming you mean the same login name? Microsoft does warn against that, as AD/Entra is known to do strange things when that is done. To cryptodan's point, this is better handled by Microsoft. These kinds of off sync issues aren't really amenable to easy fixes.

@sflatechguy, By same name, I mean same literal name and same login. However, I did find a fix for the issue, with help from another, by adding a custom attribute to AD and having Azure AD Connect Synchronization Service recognize during sync; the article is below. Basically, adding a custom attribute to AD Attributes (MSDSCloudExtensionAttribute1 {HideFromGAL}) and leaving it blank does the job (though more involved). Apparently, the MSExchHideFromAddressLists not working with MS 365 is pretty common.

Reference:

How to hide users from the GAL in Office 365 synchronized from on-premises - Jack Stromberg

Thanks to everyone for your input.