No formatting in notification emails

I’m trying to figure out why my notification emails are coming in as one blob of text – specifically no line breaks, making things hard to read. Example below:

It seemed to have started when I switched to Elastic Email for my SMTP service, but they say nothing in their system is affecting the formatting. They suggest I check the MIME type WP is sending these with, but I’m not even sure where to look for that.

Any suggestions?

The page I need help with: [log in to see the link]