I've been trying to sign up for Oracle Cloud and as part of the process an email address validation email is sent through that must be actioned within 30 mins. Unfortunately it seems if you use Zoho for email the email won't appear in your inbox till over 30 mins has passed. Very frustrating. This happens every time with a Zoho based address it seems.

I originally thought it was an issue on Oracle's side, but doing tests using non-Zoho mail providers resulted in an instant validation email coming through to action.

I also sent test emails from other accounts to my Zoho based email address and they all came in almost instantly.

What's likely to be going on here? I'd like to sign up for Oracle Cloud using my corporate Zoho mail identity rather than an alternative email account but it's proving to be impossible. Any suggestions?