My issues were with Zoho, with DKIM and SPF set up correctly. Would be interesting to see if the domain (or top-level-domain) or the e-mail provider is at fault

My issues were with Zoho, with DKIM and SPF set up correctly. Would be interesting to see if the domain (or top-level-domain) or the e-mail provider is at fault. It's difficult to test given the number of signals that are involved in flagging a message.