Event ID 12024 – Exchange Hybrid


In a hybrid mode with Exchange 2010 and when trying to send emails to on premises users the email was not getting delivered.  No bouncebacks or errors, just no delivery.

I checked out the connector from 365 to on premises and when validating the connector by setting an email address of an on premises user, the validation failed with a STARTTLS error.

The problem was I had not assigned my webmail.domain.com certificate to the SMTP service in Exchange.

After assigning the certificate – Server Configuration – Right click the webmail.domain.com certificate – Assign to services – SMTP;  email started being delivered to my on premises users.

Free/Busy Exchange Online Hybrid

We have a hybrid Exchange setup with Exchange online.  On premises is Exchange 2016.

Users who had been migrated to Exchange online could only see availability of other users and resources that were still on premises.  A check of the organization relationship showed the following;

Run the below powershell on your on premises servers and look for the FreeBusyAccessLevel setting

Get-OrganizationRelationship | fl

FreeBusyAccessLevel   : AvailabilityOnly


This was why migrated users could only see availabilty of on premises users and not any more detail.  To change this use

Set-OrganizationRelationship -FreeBusyAccessLevel LimitedDetails



Single Active Directory account not syncing to Azure AD

A single user in AD was not being synced to Azure AD via AAD Connect.  All other users were syncing just fine.  When looking at the account the attribute msExchRecipientTypeDetails was set to 2, which indicates a linked mailbox.

We used to use linked mailboxes but stopped doing so quite some time ago.  Obviously this account got missed after we migrated all users into a single forest.

To fix

set-user -identity “useralias” -linkedmasteraccount $null