Many of you are probably familiar with the “550 5.7.1 Service unavailable; Client host [x.x.x.x] blocked using FBLW15; To request removal from this list please forward this message to firstname.lastname@example.org” NDR. It has certainly been a hot topic on the Office 365 Community forums in the past few months. Up until recently, the only way to get the IP delisted was to contact Microsoft’s support and follow the instructions provided by the agent or the automatic response. While it didn’t require any particular skills or much effort, the process did take some time and caused many inconveniences to both sided.
Now, Microsoft is providing us with a self-service portal, which we can use to delist an IP. The portal is called O365 Anti-Spam IP Delist Portal and is located at https://sender.office.com/. The process is very simple – you need to enter a valid email address and fill in the captcha, after which you will receive an email with a verification link. The IP you provide on the initial page doesn’t actually need to be in the blacklist, but since you cannot change it later, better make sure you have entered it correctly. Clicking the link will take you to the next step, where you will see a single “Delist IP” button on the page. Pressing the button does the actual work, and can result in several outcomes. If the IP is not currently blocked, you will just get a message confirming this and some “redirect” information in case you are trying to delist an IP blocked for Hotmail/Outlook.com. If the IP is in the list and there are no prior offences registered, it will be delisted and you will be able to send emails from it after few short minutes. If there have been numerous offences previously, the automatic delist process will not work and you will still have to go through support channels.
Apart from the IP block problem, Microsoft is also working on providing a self-service option to delist blocked user accounts. This will soon be available under the EAC -> Protection -> Action Center page (*soon*, as in not currently available). Same rules will apply – a user can be delisted automatically, but after unspecified number of offences the process will not work and you will have to contact support. The documentation about this process can be found here: https://technet.microsoft.com/en-us/library/dn458545(v=exchg.150).aspx