SQL Server 2016 DB Mail Not Sending
On a whim, when double checking permissions, I double clicked on the actual DB mail executable. The result on the SQL Server 2014 machine was an empty command window. On SQL Server 2016 clicking the DB Mail executable presented this message:



I cannot find this requirement anywhere in the SQL Server 2016 documentation, yet it is clearly a requirement. DB Mail is functioning perfectly with no other changes than installing .NET 3.5.