Office 365 IP Black listed and email marked spam by Yahoo/AOL

Thanks for the detailed response. 

I think the reason why people opt for cloud mail solution like office 365 has to do with the fact that they don't have to worry about the underlying infrastructure and deal with issues like IP blacklist. If the IP was owned by us or was a dedicated Ip assigned just for our use, then I agree it should be us contacting Yahoo. However, this is not the case and we are just one of your many users using that IP. 

If going by the case customer should contact mail providers to get Office 365 IPs whitelisted is quite unpractical. Firstly, the IPs are owned by Microsoft and customer don't have any control over. Secondly, the IPs are dynamic and shared with multiple O365 customers. Therefore, we need to ask Yahoo to unblock a million IPs used by over billion users. I don't think any provider would do that. Thirdly, as a basic condition for removing from the blacklist, most of them ask for a declaration stating that no more spam email will be sent from the IP. How can anyone provide such declaration for IPs owned by Microsoft and shared with a million customers?

Further, this is not a case of a few random IPs, almost all emails send to yahoo are going to spam and each has a unique IP that is blacklisted. Since Yahoo/AOL is still one of the prominent email providers out there, this should be affecting many Office 365 users.  I believe this is something Microsoft should deal with Yahoo rather than asking the customer to deal with it.