Is there a way to make sure sent e-mails are opened?

A few years ago I decided to ditch Gmail and started using Disroot as my e-mail provider. It was recommended by privacytools.io.

I realized that at least one e-mail I sent went to spam and now every time I send an e-mail I get paranoid if it will reach its destination. Is there a way to know if the e-mails I send are opened?

I've thought about switching to a more mainstream e-mail provider like ProtonMail but I already have so many accounts linked to Disroot that make switching dreadful. As a matter of fact I still have over 100 accounts that are using my Gmail address because it's so time intensive and not a priority to do the switch. Hopefully in the password-less future this kind of problem will cease to exist.