So I tested this with https://emailprivacytester.com/. I didn't get an automated response with a link. However, I noticed that somebody had viewed the email using an iPhone. So I scanned my logs to grab the referer from the callbacks and it was:
Thanks for your testing! We have fixed the script / meta tag strip problem. We keep improving our code base, making sure emails are rendered correctly on web pages. We won't use user data for anything else.
http://mailp.in/dashboard/reply/*ID*
Where I replaced the actual id with "ID". So I copied the ID from that referrer and visited:
http://mailp.in/*ID*
It seems you don't strip out quite a lot of stuff, including script tags and meta refresh tags.
If you want to contact me about any of this, my details are at https://grepular.com/#contact (I am the author of https://emailprivacytester.com/ if you hadn't guessed)