Symptoms
If you use Set-CasMailbox to set the ActiveSyncSuppressReadReceiptparameter to True, read receipts are not automatically returned if the user opens an email message that was sent by having a read receipt request set. However, the read receipts are still automatically sent if the recipient of the original message replies to it or forwards the message to another person. In this situation, a read receipt is sent even if ActiveSyncSuppressReadReceiptis set to True.
Resolution
To fix this issue, install the following cumulative update:
Cumulative Update 14 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019
