The domain name doesn't matter at all. The really important thing is the IP of your MTA (the server sending mails). Eg. if it was previously used to send spam you need to get a new one from your server provider, as it will be blocked everywhere. Also the server configuration needs to be good. Use dkim, dmark, spf, mta-sts, etc.
I don't agree with this hard split between SPAs and MPAs anymore (ie. SPAs for apps, MPAs for websites/content). In my opinion SPAs are simply a progressive enhancement for MPAs which allow even faster page navigation. All frameworks now come with SSR solutions and if a website still requires JS to show content that's a skill issue.
Looking at Astro the line between SPA/MPA is getting really blurry. Just slap a View Transition element on your page and you got a MPA which acts like a SPA when JS is enabled.
Logic doesn't work for people trapped in a cult. They can claim whatever they want and don't need to admit anything, it doesn't matter. 😔