What mail function is used to send the subscription notificaitons?

Hi Support, we're using the Subscribe by Email plugin on one of our websites. We are still running version 1.1.5 because we did a ton of custom work to it.

Can you tell me what mail function version 1.1.5 uses to send the subscription notifications? Does it use wp_mail or something else?

And, can you tell me what mail function version 2 uses? Same question.

We ask b/c we have about 12,000 subscribers, and we needed to connect our blog to Amazon SES (Simple Email Service). And we're using the WP SES plugin to do it (http://wp-ses.com/).

Any advice or thoughts you can provide are greatly appreciated.

Thank you!

- Dave