@aral @cancel I can very much relate to that. During my masters final project, the team and I developed a phishing platform and we found out that it was *really* hard to get e-mails sent to the end inbox, especially on some providers.
Debugging this case is hell as those o365, and other providers, blackbox are just meant to keep their advantage and force users to them.
Later as a pentester in charge of most phishing missions, I found out that Google was from far the worst.