I have begun work on a custom email plugin, and while looking at some others that are available to see how they went about things I noticed that all of the available plugins (at least that I have found so far) already have an entry in the email setup list, regardless of if you have downloaded the associated plugin for that service (ex. Sendgrid, Mailgun, etc).
So my questions is, if I have a custom email plugin, how exactly would I go about making it selectable / usable by the forum? Does it need to be present in the default email list? Is there a way to have my plugin inject itself into that list of providers or is there a way to override that list so that the forum knows not to use the credentials and settings in there, but instead use the ones in the plugin?
The only real switch I have found is the "Use an external email server to send emails", which I would imagine that if it is turned off, that would not be much help either.
If anyone has any insight on how the system works in regards to this and can point me in the right direction, I would appreciate it!