Malcolm Roberts

.netcore 2.0 has the ServicePointManager class. Looks like you'd set the [ServerCertificateValidationCallback](https://msdn.microsoft.com/en-us/library/system.net.servicepointmanager.servercertificatevalidationcallback.aspx) on it ```C# ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, sslPolicyErrors) => true; ```

Also, if you want to disable SSL, on the current version you have to set the UseSsl flag on the SmtpSender class. It overrides the SmtpClient setting.

Are you setting up a default sender? It might be helpful to create a `UnitTestSender` that just adds the emails to some list you can check in your test?