@Revan6
I use zoho, which receives email from our site just fine.
I think datamine uses inbox, which also works.
Outlook typically works as well, though you have to whitelist us to prevent from going to spam.
Yahoo gives mixed results.
Gmail blocks us. They don't like our email headers for some reason ... something about the domain not matching sender's IP or something ... no idea how to fix it. As far as we can tell, everything matches up and is legit.