In Microsoft Exchange Server 2019 or Exchange Server 2016, assume that you enable attachment filtering on Edge Transport servers to help prevent files in email messages from entering your organization. When you receive an external email with attachments and a digital signature, you could see the following error message:
"There are problems with the signature. Click the signature button for details."
This issue occurs because the attachment filtering does not process the email correctly.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
To fix this issue, install one of the following updates:For Exchange Server 2019, install the Cumulative Update 1 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.