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

Hey Tharun Jacob George,

So looking at the link you gave me to check the IP I only see it on one blacklist - backscatter.

Backscatter is one of the more... frustrating blacklists to deal with. When your IPs get listed there, essentially there response amounts to this - "well we have allot of information to go through, and we are unsure if your IP is now safe. If you want to pay us some money, we will expedite your review, which if you are good will result in you getting removed much quicker. If not we will continue to review logs and remove any IPs we feel are now safe in due time."

Now they cant outright keep IPs on there that are safe, especially ones from companies like O365, but they are just kind of frustrating to deal with. From the perspective of someone who has been involved in the higher up technical aspects of a multiple million mailbox hosted system, backscatter was the blacklist we liked the least.

The fact that the IP itself is not listed anywhere else, tells me the IPs are in a fine state. So now on to why Microsoft said what they said. If this was just a server a random IT shop was running for you, then the owness would somewhat fall on them. But they would just reach out to yahoo and say hey we are not spamming what can we do to help, and it would be up to yahoo to make changes. In this case, Microsoft is saying they have done everything to ensure their IP is in a good state, and from looking at the blacklist check, atleast for this IP, I agree with them. 

The reason you got the response from Microsoft, is because of the tag you got back from Yahoo indicating that they flagged your message as bulk. In essence Yahoo is taking an active step to blacklist that IP/message.

Because this is a decision by Yahoo, and for all intents and purposes to Microsoft the IP seems fine (again backed up by the fact that the IP is in essence not listed anywhere but backscatter,) then there is nothing Microsoft is going to be able to do for you.

I would contact yahoo from your account, say that the message got filtered out, and that it is legitimate mail. From what I can tell, yahoo seems somewhat trigger happy applying their own "bulk" tag to ip's messages.

Additionally O365 uses an absolute metric ton of ips. The chances that you will be sending from the same server for all your users, or systems, over any extended period of time is just not likely. I would test again to see if you get the same error.

Finally as a closing thought, this wont stay for long as its just bad business for yahoo. The most recent number i can find is from over a year ago stating that O365 had 120 million users. I am sure that had grown allot since then. - https://www.zdnet.com/article/microsoft-office-365-now-has-120-million-business-users/

If Yahoo is blacklisting O365 ips, they are essentially running the risk of their users not getting mail from any of those millions and millions of users. In the world of email, the gorillas can kind of set their own rules, as long as they are mostly reasonable. Well in this case O365 is not just a gorilla, its King Kong.

I do not expect that IP to stay listed on yahoo for long. Additionally I think you should have luck getting different IPs, and if you wanted to force the issue, you could setup your outbound server in outlook/application to be hardcoded to an IP. (use smtp.office365.com or something like that instead of automatic). And last but not least, if you want to try to work this out through IT support, you will need to go through yahoo, as they are the ones actively taking measures to block it. They may be willing the white list the IP for your user/domain, they may be willing to take action system wide knowing its O365, but since they are the ones specifically doing something to stop the message, they are the ones who will need to intervene to fix it.

Adam