Forum Discussion
Event ID 5000 - MSExchange Management Application
salimhurjuk it seems the Discovery Mailbox is missing. Check this and in case re-create it.
https://learn.microsoft.com/en-us/exchange/architecture/mailbox-servers/recreate-arbitration-mailboxes?view=exchserver-2019
First check if it really misses.
For the setup use the same version you're actually running (identical CU). Neither use an older one nor a newer. The setup "stamps" the Active Directory ("E:\Setup.exe /IAcceptExchangeServerLicenseTerms_DiagnosticDataON /PrepareAD"), it doesn't start a setup of Exchange but re-creats missing systen accounts e. g. You have to have the right privileges to run this command (I think schema admin, I'm not sure).
Then you just enable the discovery mailbox described in the link i sent before.
This should have no impact on your running system at all.
Deleted
I have this many SystemMailBox Accounts.
This is a discoverysearchmailbox I can see AD
salimhurjuk Since the Discovery Mailbox (starting with ID e0dc1c29) exists, the pre-described steps might not help, except the Discovery Mailbox is damaged. At this point I'm not close enough to gather more information or provide more substantial help.
Hope, someone else could.