Here’s a video demo of how you can incorporate YouTube videos and lists of blog posts into your event promotion / event replay emails as well as other types of email newsletters using the RSVP Mailer component of RSVPMaker for WordPress.
Key components of this solution include, a way of importing the content of entire posts into the email template.
I applied that technique to this content, creating the blog post first and then using it as the basis for an email to my list.

An alternative is to use the RSVP Email Embed Post or Posts content block to display excerpts of a chosen post or a listing of recent posts from all categories or a single category. Other recent posts blocks or shortcodes may work in the email template, but I recommend testing them first. This one is tested to work with the RSVP Mailer methods of formatting email.

Although not shown in the video, you can of course also include RSVPMaker blocks for displaying event listings …

… or promos for the next few events / events in a category.

To style the background of the email template, select the email body block that wraps around the other content.

For best results sending to large lists, I recommend taking advantage of RSVPMaker’s new integration with the Postmark email sending service.