Symptoms
If you set a large port number, such as 55222, as a send port of the SFTP adapter, the host instance that runs the port logs the following exception in the Application event log:
System.ArgumentException: Port number cannot be negative
Resolution
The fix that resolves this issue is included in the following update for BizTalk Server:
Cumulative Update 5 for BizTalk Server 2016
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about service pack and cumulative update list for BizTalk Server.
Learn about BizTalk Server hotfixes and cumulative update support.