Issues delivering to

You are reading this article because you have received a bounceback claiming your IP is blacklisted.

We have had isolated reports that emails being sent to Microsoft based domains such as, and are being rejected by Microsoft and bounced back. 

Before we roll into the exact issue, there are currently two solutions to getting emails delivered to Microsoft based domains from Rackspace mail hosted accounts.

OPTION 1 - simple

We have found that by logging into webmail at your emails will be delivered to MS as the IP's used by the webmail system are inside a different IP range than the ones used by email clients.

OPTION 2 - advanced

We have created a free solution by setting up a separate SMTP server outside the Rackspace environment which allows messages to be delivered through our private IP. This does involve you updating your SMTP setting in your email devices.

You can view that solution here: 

Why is this happening and what's being done to resolve it?

The Rackspace mail system is hosted on hundreds of revolving IP addresses and occasionally a spammer slips through the net and starts sending out spam from one or more of the IP's. When that spam hits a Microsoft address and the user reports it as spam, Microsoft puts a hard block on the IP address and email from the IP can no longer be delivered.

This is why a small number of our clients are being affected.

Our upstream provider, Rackspace, is working with the Microsoft spam team to resolve the issue but there is no given ETA so in the meantime we have the options given above.

Update 30th of June 2021
Fixing this issue is our top priority. Our entire developer and engineering group has been partnering with our Incident Management team and actively working on fixes for the underlying issue. We’re rolling out changes to mail routing and anti-abuse systems multiple times a week and we are in constant communication with the team at Microsoft responsible for the listings, as well as their leadership team, and continue to make adjustments daily. We have seen significant improvements, but we still have some work to do, and I can not provide a full resolution on this.

Additional Resources
MS keeps blocking emails from Rackspace, who we use for our businesses' emails.
Rackspace MX Blacklisted by Microsoft
Issues delivering to
Rackspace Outgoing Email failures

Office 365 Anti-Spam IP Delist Portal
New support request for

  • rackspace mail, outlook deliverability issues, office365
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