WP Mail SMTP

It should work, but I can’t claim to have tested it. If you leave the email server settings for RSVPMaker blank, messages get sent through the WordPress wp_mail function that various SMTP plugins hook into.

I’m currently looking for beta testers for an integration with Postmark, an economical email sending service that allows RSVPMaker to be competitive with Mailchimp and MailPoet if you like the email authoring environment.