Symptoms
Assume that you use SQL Server 2017 on Linux. If you configure the Transmission Control Protocol (TCP) port where SQL Server listens for connections to a non-default value (the default value is 1433), SQL Server Database Mail may be unable to connect to SQL Server. Therefore, you cannot perform database mail operations.
Resolution
This issue is fixed in the following cumulative update for SQL Server:
Cumulative Update 6 for SQL Server 2017
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
Latest cumulative update for SQL Server 2017
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about the terminology that Microsoft uses to describe software updates.