Microsoft Outlook blocking emails from Linode

There is apparently a problem in the Microsoft Outlook network that started on or around 22 December 2021 resulting in emails sent from Linode servers being rejected with:

550 5.7.511 Access denied, banned sender

Some discussion of the problem can be found here:

• 550 5.7.511 Access denied, banned sender
• Trying to find help for 550 5.7.511 Access denied, banned sender
• 550 5.7.511 Access denied, banned sender - Office 365

From the above discussions it appears to impact Linode-hosted mail servers regardless of past email- or spam-related activity.

All we can suggest at this time is to follow the instructions in the 'bounce' emails by forwarding them to and perhaps at the same time submitting a ticket to Microsoft Support.

Update: Linode have informed us that they are "still working with Microsoft regarding the "550 5.7.511 Access denied, banned sender" error and are treating this problem with the most urgent priority."

Update: Microsoft has pointed us to Microsoft Support for business where affected businesses can submit a support ticket.

Update: As of 9 February only one of or servers remains blocked. We are working on getting the last one de-listed as well.

Update:19 February and emails are flowing normally again.

Related link

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

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