Microsoft email blacklists – why many people are unable to send to Hotmail.

It has been brought to our attention in recent days that there are now several accounts from other hosting companies and email providers of emails to, and being blocked from delivery due to Microsoft’s own blacklists.

This is not wholly uncommon. Microsoft have blocked several email servers in the past (e.g. NHS blocked by Microsoft)

The effect? Any email originating from a blocked IP address will be refused delivery. This can effect entire ranges of websites, domains and even data centres.

The cause? Microsoft’s “Spam Report” facility (e.g. in Hotmail) has been alerted that a particular IP has been sending Spam emails.
This could be genuine SPAM originating from a Spam attack. There have been recent spates recorded at several data centres of huge SPAM attack storms where Spammers attack mailboxes to compromise access and use the mailbox to send huge volumes of Spam.

3rd Party blacklists are used all around the internet and management of listing/de-listing against these lists is an important, yet laborious task, requiring regular vigilance to ensure maximum send reliability.

At teclan we are very proactive when any of our IP addresses are listed. We perform daily blacklists checks to ensure our sending servers’ reputation is maintained as highly as possible.
In situations such as Microsoft blacklisting IP addresses all we can do is to resubmit a Microsoft de-list request and wait for removal from this list.

We can also offer alternative sending services to our hosting clients to ensure they can avoid this issue whilst the blacklisting continues.

If you are a hosting customer of teclan’s and are experiencing email issues like the above then please get in touch with the team who will be able to assist you.