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.

According to Microsoft Support, there's a bug in SQL server 2016 Setup that causes the database mail not to work without .net 3.5

There's a work around by creating a DatabaseMail.exe.config file in the same folder where the DatabaseMail.exe exists (Binn folder) write the following to the file and save with utf-8 encoding

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<startup useLegacyV2RuntimeActivationPolicy="true"> 
<supportedRuntime version="v4.0"/>     
<supportedRuntime version="v2.0.50727"/>
</startup>
</configuration>

Source: FIX: SQL Server 2016 Database Mail does not work on a computer that does not have the .NET Framework 3.5 installed

Take alook at this instead. This way you only need to copy a file instead of installing .net 3.5. Need to install CU1 first. Check here for more details.