Some of the deliverability issues are the result of sender-based software configurations.
You can find the current list of our MTAs by querying "nslookup –q=mx hotmail.com" from a command prompt (this should work in a variety of Operating Systems).
Currently, the addresses for these servers are mx1.hotmail.com, mx2.hotmail.com, mx3.and mx4.
This is the practice of verifying email addresses without sending (or attempting to send) emails to those addresses.
This method is commonly used by malicious senders to generate lists of valid e-mail addresses that they can send spam, phishing emails or malware.
Smart Screen® email filters are influenced by a number of factors related to the sending IP, domain, authentication, list accuracy, complaint rates, content and more.
Of these, one of the principal factors in driving down a sender's reputation and deliverability is their junk email complaint rate.
We may not accept email from senders who fail a reverse-DNS lookup.
In some cases legitimate senders advertise themselves incorrectly as a non-internet routable IP when attempting to open a connection to
IP addresses that are reserved for private (non-routable) networking are 192.168.0.0/16, 10.0.0.0/8, and 172.16.0.0/11 (or 192.168.0.0 - 192.168.255.255, 10.0.0.0 - 10.255.255.255, 172.16.0.0 - 1.255).