Microsoft has its own internal blacklist, the precise mechanisms of which are not known; in addition to the sending of spam, inclusion in this blacklist can also occur for a single domain also for a considered anomalous (but not necessarily massive) sending of emails to addresses @live.com, @hotmail.com, @outlook.com etc.
Therefore, if you receive notifications of failure to send to Microsoft addresses, it is necessary to proceed with a "targeted" delisting of your IP and domain.
- Open an anonymous browser session, and take care NOT to be authenticated on Microsoft services
- access the following pages: https://support.microsoft.com/en-us/getsupport?oaspworkflow=start_1.0.0.0&wfname=capsub&productkey=edfsmsbl3&locale=en-us&ccsid=636245014246660198
- fill out the form carefully
In addition to this, it may also be helpful to register for the Microsoft Smart Network Data Service (SNDS) program
