Email blocklisting: A Christmas gift from Microsoft that Linode can't seem to return

Sorry, that IP address is on the naughty step


Microsoft appears to have delivered the unwanted Christmas gift of email blocklisting to Linode IP addresses, and two weeks into 2022 the company does not seem ready to relent.

Problems started as large chunks of the world began packing up for the festive period. Complaints cropped up on Linode's support forums when customers began encountering problems sending email to Microsoft 365 accounts from their own email servers.

On that thread, a Linode staffer acknowledged there was an issue and suggested a number of alternative third-party email services as a stopgap as well as saying: "Microsoft has acknowledge[d] the problem and looking into it [sic]."

More recently, the Linode team has offered to swap out affected IPv4 addresses for unaffected ones – or, for a fee, it will add some new ones to users faced with the problem. "While we cannot control how long it takes for Microsoft to address the issues on their end," said Linode, "we do have potential solutions that we can offer in order to help customers avoid the current 'Banned Sender' bounces."

The question also cropped up on Microsoft's own forums as users queried banned sender bounces for emails from Linode IP addresses. "Most of our clients but not all hosted with Microsoft don't get our emails because of this issue," posted one user.

Blocklisting IP addresses to prevent the delivery of unwanted emails is not a particularly complicated concept, although Microsoft has perhaps been a little more enthusiastic about this than is strictly necessary over the years. In 2019, tsoHost's bulk email domain found itself on the naughty step for Outlook and Hotmail addresses and getting itself off again proved a bit of a challenge.

Linode itself is an infrastructure-as-a-service outfit, with data centres spread around the world. One can host one's applications (including email services) and data on its platform as an alternative to the bigger boys. Right up until Microsoft decides to slap the IP addresses one is sending from on to a blocklist.

It should be possible to get the addresses removed, but users have reported issues. "Requesting to delist via their automated portal doesn't work as it claims the IPs aren't blocked," said Register reader David Bennett.

"I personally have half a dozen servers with them and the only way I'm managing to get any progress is opening tickets as I'm also a 365 customer and requesting escalation until I finally find someone who has access to the super-secret list.

"It's a really hefty problem for tons of businesses, charities etc, given how many folk use 365 for their email and how many sites rely on being able to send emails to them!"

It certainly highlights just how many people have handed the pain of running their email to Microsoft in the last few years. All well and good until something gets added to the blocklist and can't be scratched off again.

The problem seems to be easing a little in recent days – some Linode users have reported that after begging, pleading, and escalating (like our reader) some IP addresses have been released. Others, however, remain resolutely out in the cold.

As one sad little posting on Linode's forums put it: "As [with] many things Microsoft, it seems somewhat arbitrary what [sic] they react to or not."

And Bennett? "One of our ones that had been fixed is now blocked by Hotmail instead... sigh."

The Register contacted Linode for its thoughts on the matter.

A spokesman said the issue was "currently the number one priority for our Trust and Safety team. We're iterating on changes we think are going to help address this, and have been working with Microsoft to identify the issue and get it solved as quickly as possible. Our community team will update the thread as soon as there is a resolution."

We also asked Microsoft for its take. We will update this piece should it respond. ®

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