We currently run our Exchange servers in house and have our email filtered by Appriver but plan to move to Office 365 soon. I used to be really happy with Appriver's filtering but as of late it's hasn't been as effective. The CEO gets that quasi-spam that is hard to catch and wants to reduce that. The only way I see that happening is allowing whitelisted emails only. In the past I've run across some companies that automatically respond with a challenge email to confirm that this is a legitimate email to add the person to the whitelist. Is there an option for this in Office 365 to have one mailbox accept messages in a similar fashion?
Appriver only filters our incoming email and in the past people have asked if our outbound email helps build/train the spam filters to which the answer was no. Does Office 365 learn from your outbound email...