I have a WordPress website recently migrated to new dedicated hosting. I can’t make any SMTP plugin work: no matter which one I try, my admin-ajax.php keeps loading and loading… this is causing also my website to stop working (all the forms just won’t submit).
I have contacted my hosting company and they can’t see any issue in there. Upon checking, I found this error: “AH01630: client denied by server configuration: [MYPATH]/index.php, referer: http://[MYWEBSITE]”. Strangely, the “referee” is a HTTP URL, but my website is in HTTPS.
I believe it’s a CORS error, but I can’t really make it work.

I have tried WP Mail SMTP, FluentSMTP and others and still no luck. A plugin I have tried once didn’t cause the error in question, but was returning a “can’t connect to the host” generic message.

Any help you can give me, will be much appreciated.