Recently Hotmail started to reject emails coming from our domain , giving following error.
Error transferring to mx4.HOTMAIL.COM; SMTP Protocol Returned a Permanent Error 550 SC-001 (SNT0-MC2-F23) Unfortunately, messages from xxx.xxx.xxx.xxx weren't sent. Please contact your Internet service provider since part of their network is on our block
I checked at mxtoolbox.com website mail server blacklist checker and all over the internet in all possible dns black lists but my IP address was not listed and it was clean. I then signed in to Microsoft Smart Network Data Services at https://postmaster.live.com/snds/ and found out that my IP address was in Hotmail black list.
I found out that Microsoft has an Eform for De-Listing / removing spam black listed mail server IPs not able to deliver to Hotmail and live.com.
Fill out the below form
It will ask you Contact name, Contact e-mail address, Enter your Email Server Public IP in Outbound IP(s) or range(s) and submit, You will receive an ticket number and it may take upto 2-4 days for your request to be entertained. Hopefully they will remove it from there black list. It also happens if you sent email to any user and he mark it as junk/unwanted then it auto adds in Hotmail monitoring system.
TIP- 1: Using Internet Explorer I receive an error has occurred while submitting the above form, After using Firefox I was able to successfully submit the form.
More info can be found here.
TIP- 2: In such situation when your public ip added to black list, you can use your ISP smtp/smart host to relay mail. This way your ip wont be used and usually ISPs maintain there mail relay system upto date.