After sending a campaign you can get a preview link of the email sent. We use that share with people who weren't on the mailing list but want to see the content. But the url is pretty ugly and some people come back and say it looks dodgy. eg:
http://x2qq4.mjt.lu/nl2/x2qq4/57y25.html?hl=en

Could you give us a "prettier" url with a more legitimate looking domain name and then use the subject or campaign name to make it more friendly. This is an example of one we had with Mailchimp:

https://mailchi.mp/progression/2020-foiling-and-wave-camp-dates-6104509

Cheers