[magashna]

Confirming your emails are getting through to providers like gmail is the hard part

[megous]

It's not the hard part, it's simply impossible to ensure from your side. You can have everytrhing righy, and they'll still block you based on IP address.

[shirro]

You can configure your dmarc so the big mail systems all provide you with reports on delivery failures. I get lots of them when I reply to a mailing list that doesn't deal with spf or dkim sensibly.