Assume that you install Microsoft SQL Server 2016 on a computer that has the .NET Framework 4.6.1 installed. If the computer does not have the .NET Framework 3.5 installed, the Database Mail feature does not work correctly. For example, if you configure and send a test email message, the message is queued but is never sent.
This problem was fixed in the following 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: