That looks like the standard Office365 "you got listed" message. Even
legitimate B2B bulk mail will now and then generate these. Just follow the
instructions; delisting is straightforward. If it recurs, of course, you
might have a troublesome mailer on your hands.

John


On Mon, Jun 25, 2018 at 12:24 PM, Josh Campbell <[email protected]>
wrote:

> Has anyone else noticed these errors? We hadn't really seen them
> previously. They look like this:
>
> smtp;550 5.7.606 Access denied, banned sending IP [xxx.xxx.xxx.xxx]. To
> request removal from this list please visit https://sender.office.com/
> and follow the directions. For more information please go to
> http://go.microsoft.com/fwlink/?LinkID=526655 (AS16012609) [
> AM5EUR03FT031.eop-EUR03.prod.protection.outlook.com]
>
> We've only started seeing them in the past month and only a small amount
> of IPs have been affected at any one time.
>
> The interesting thing is all of these IPs are in the same IP range (out of
> the three major ranges we have).
>
> I'm wondering if this is a new phenomenon for anyone else and why it only
> appears to affect one of my IP ranges. (Also, if anyone from Microsoft
> cares to get in touch, I'd love to hear from you.)
>
> Josh Campbell, Deliverability Engineer
> MailChimp
>
>
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>
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