Symptoms
Users whose mailboxes were recently migrated from on-premises Exchange Server 2016 to on-premises Exchange Server 2019 in the same organization no longer receive daily mail quota warning messages if their mailbox reaches the maximum message limit. After the migration, these users do not receive the warning message until about one week after they reach the limit.
Resolution
To fix this issue, install the following update:
Cumulative Update 11 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019
References
Learn about the terminology that Microsoft uses to describe software updates.
