Managing the email connections to and from your WordPress website can get tricky and confusing if 1) you need to configure a connection that is not the basic, default configuration supplied by your hosting provider, and 2) you're not an expert in the field of computer network protocols.
As with many things "WordPress", the easiest way out of a potential configuration quicksand is to let a plugin handle the issue. However, when it comes to server-oriented configuration, the majority of helpful plugins are of the premium kind. Furthermore, you often end up having to work just as much to make the plugin work the way you want as you would if you performed the entire setup manually in the first place.
FluentSMTP is a nice little email configuration plugin that's both easy, full-featured, and free. For an overview of the plugin functionality, you can watch WPCrafter's video on the subject here.