Ionos, the hosting company formerly known as 1&1, has found itself on Microsoft's naughty list as emails from its servers won't reach Outlook.com accounts.
Problems appear to have been ongoing since 09:46 BST on 20 August, according to Ionos's status page.
More than 48 hours later, engineers are still working to resolve the issue, which, judging by the emissions from the company's support orifice, requires some cooperation from Microsoft.
Hi, apologies, we are still working with Microsoft to have this issue resolved - Our status page will be updated once we have feedback - Thanks ^na— 1&1 IONOS UK Support (@ionos_help_uk) August 22, 2019
The outfit's German arm was a little blunter. Responding to a message from a user that included a helpful screenshot indicating that at least part of Ionos's network was on Microsoft's block list, it suggested trying to "send more often" since some servers weren't on Redmond's naughty step.
Which could well be how the company found itself in this situation in the first place.
The impact on customers has been severe, with many relying on emails getting to their destination to, you know, actually do business.
Latest update from @ionos_help_uk come on guys, what's occurring?— British Travel Award (@BritTravAwrds) August 21, 2019
Now 4,823 and counting auto-response emails bounced back to our inbox... great start to our day!
All #voteBTA19 systems are operating normally and votes recorded but voter confirmation emails bouncing. pic.twitter.com/FAVlOWNeO2
While standard email is not a guaranteed delivery medium, a user would be forgiven for expecting at least some emails to make to it to a Microsoft destination. In our testing from an Ionos account we found that Gmail would happily accept messages. Outlook.com was less keen.
Of course, it isn't the first time the company has fallen foul of Microsoft's block list, and it joins the likes of TSO Host (a company that claims to know hosting "back to front") in finding its IP addresses blacklisted by Redmond.
It has taken TSO Host more than three weeks to get its IP addresses delisted from spam watchdogs, such as the Spam Open Relay and Blocking System (SORBS).
Ionos users will hope that the Montabaur-based web hosting provider will resolve the issues a little faster. Again.
Several hours after we asked, the eager beavers at Ionos finally gave us a statement, and we're happy to share it: "We are currently observing issues that may occur with the delivery of emails to mail accounts managed by Microsoft. We are working with Microsoft to find a solution."
So there you go.
We also contacted Microsoft for its take on the situation and will update if we get a response.
Thanks to reader Richard for the tip. ®