SentToMemberOf shows every recipient type not distribution groups when you create transport rule in Exchange Server 2019 and 2016

Symptoms

When you create a transport rule (mail flow rule) and select the SentToMemberOf (is member of this group condition) parameter, it should show only the distribution groups, dynamic distribution groups, or mail-enabled security groups. However, the list shows everything including normal mailboxes, contacts, linked mailboxes, and every recipient type.

Cause

The filter that’s used in this scenario isn't correct.

Resolution

To fix this issue, install one of the following updates:

• The Cumulative Update 3 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.

• The Cumulative Update 14 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.

References

Learn about the terminology that Microsoft uses to describe software updates.