Symptoms
Consider the following scenario:
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From Microsoft Office 365, you send a message that has an attachment whose file name ends in .com.
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Office 365 Journal attaches that message to a journal report.
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The Journal report is sent on-premises to an Edge server by having the Attachment Filtering Agent enabled.
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The Edge server checks the attachment and discovers that its name ends in .com.
In this scenario, the Attachment Filtering Agent removes the attachment before the message is sent. The agent strips out journaled attachments that end in .com, .exe, or .cmd.
Resolution
To fix this issue, install Cumulative Update 13 or a later cumulative update for Exchange Server 2019.