Send message to a patron using an API

Is there any way to send a user a message programmatically?
My use case is as follows: When a new patron subscribes to my campaign (if that’s the correct term? Becomes a new patron), I want to send them a message containing a single use activation code, allowing them to create a new account on my website.

This activation code must obviously also be registered by my server, and must be unique for each user.
Allowing me to send messages to my patrons programmatically would solve this issue.

Is this possible?
Or is there an other way to solve this?

That wouldnt be possible via Patreon using the API. However, if you sync your patrons to your site, you can then automatically send a message to that patron via the patron’s email through your site.

Do you have any links/tutorials/instructions of how to achieve this?
Or do you just mean that I can send them an email without using patreon infrastructure?

Yes, I meant that when you sync your patrons to your app, you can trigger an email (through mailgun, sendgrid or whatever mail service you are using) to send them an email from your app/site.