S/MIME signed reply draft behaves like the first message in conversation in Exchange Server 2019 and 2016

Symptoms

In Microsoft Exchange Server 2019 or Exchange Server 2016, consider the following scenario:

• User A sends an email message to User B.

• User B composes a reply by adding a S/MIME (Secure/Multipurpose Internet Mail Extensions) signature.

• User B saves the reply as a draft.

In this scenario, you find that the draft of the reply does not have a value for the InReplyTo property.

Resolution

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

For Exchange Server 2019, install the Cumulative Update 3 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.

For Exchange Server 2016, install 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.