Exchange 2013 to Exchange 2019 with DAG (MapiExceptionNoSupport 0x80040102)

You are running a Exchange2013 DAG

DAG2013
`-Exchange2013ServerA
  `-DB2013-01, DB2013-02 (passive)
`-Exchange2013ServerB
  `-DB2013-02, DB2013-01 (passive)

and want to move to 2019 but you are like this

DAG2019
`-Exchange2019ServerA
  `-DB2019-01
`-Exchange2019ServerB

Test-MAPIConnectivity -Server xchange2019ServerA failes with long ROG trace, you cannot get a healthy replication or Eventlog Shows Database Errors, but the essence is:

[Microsoft.Exchange.Data.Storage.NoSupportException]: Cannot open mailbox. There is no support for this operation. Inner error[Microsoft.Mapi.MapiExceptionNoSupport]:MapiExceptionNoSupport: Unable to open message store.(hr=0x80040102, ec=-2147221246)

Please note, this post ONLY covers 0x80040102 && MapiExceptionNoSupport. Other combinations with very similar traces have different solutions!

There is not much information about this online and most of it seems to just magically work after a reboot.

The problem seems to be here: Get-MailboxDatabaseCopyStatus |fl name,*schema*

Name                                  : DB2019-01\Exchange2019ServerA
MinimumSupportedDatabaseSchemaVersion : 0.121
MaximumSupportedDatabaseSchemaVersion : 0.185
RequestedDatabaseSchemaVersion        : 0.121

RequestedDatabaseSchemaVersion is too low. The Ex19 Server seems to be unable to run this Databases any longer.

However Update-DatabaseSchema -Verbose -Confirm -Identity DB2019-01 -Debug does neither return an error nor update the database.

Using ECP with ?ExchClientVer=15.2 does not create a 0.185 Version Schema.

Using New-MailboxDatabase on the command shell does not create a 0.185 Version Schema.

Rebooting the server, restarting replication and information store does not change the situation.

Problem: See: https://interoperability.blob.core.windows.net/files/MS-OXCMSG/%5BMS-OXCMSG%5D.pdf

and the trace

Microsoft.Exchange.Migration.MigrationDataProvider.CreateProviderForMailboxSession(MigrationADProvider activeDirectoryProvider, MigrationFolderName folderName, Func`2 mailboxSessionCreator)    at Microsoft.Exchange.Migration.MigrationDataProvider.CreateProviderForSystemMailbox(Guid mdbGuid)    at Microsoft.Exchange.Migration.MigrationServiceFactory.CreateProviderForSystemMailbox(Guid mdbGuid)    at Microsoft.Exchange.Migration.MigrationJobCache.<GetMigrationCacheEntriesForServer>d__20.MoveNext()|GetMigrationCacheEntriesForServer: Error 
accessing system mailbox:

Suggesting a (imho) serious Exchange 2019 bug. It allows you to create Databases in an old schema, tries to migrate them and locks you out.

Solution: Exchange2019 falls back to MinimumSupportedDatabaseSchemaVersion because the of the old DAG Cluster.

1. Remove at least one Exchange 2019 Servers from the DAG.
2. Make it have all databases mounted
3. Update the Database, create a new one or wait until Exchange19 will do it for you. (This is, why it works for some people with reboots)
4. Join the DAG again