The mailbox GUID of an external system mailbox *** does not match the information in the Active Directory for the mailbox - Event ID 7043 - Exchange server Error

The mailbox GUID of an external system mailbox *** does not match the information in the Active Directory for the mailbox - Event ID 7043 - Exchange server Error

The below event will get generated when you have duplicate system mailbox in the Exchange server

Name: Application
Source: MSExchangeIS Mailbox Store
Event ID: 7043

Description:

The mailbox GUID of an external system mailbox ('Mailbox - SystemMailbox{bcedee61-d318-4dbb-b168-d89a275ce596}') does not match the information in the Active Directory for the mailbox. The existing GUID ('efc150c4-04e3-41e5-99cb-9dd193524e1e: /o=First Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=SystemMailbox{bcedee61-d318-4dbb-b168-d89a275ce596}') has been replaced with the expected GUID ('197a4757-c7ea-45e7-a8ec-d6d7116497c9: /o=First Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=SystemMailbox{bcedee61-d318-4dbb-b168-d89a275ce596}').
Solution:

1. Backup Active Directory
2. Open the Active Directory Users & Computers
3. Click the View menu at the top and check “Advanced Features”
4. Expand the “Microsoft Exchange System Objects” container.
5. Matched the GUID which we see in the event deleting the duplicate GUID.
6. Wait for few hours for replication.