MSFT reverse IP failure?

Tue Feb 27 00:46:21 UTC 2018

On Tue, Feb 27, 2018 at 11:04 AM, Ken Chase <math at sizone.org> wrote:

> Im not exactly sure what this is either, the client sent me a screenshot
> that called itself the "microsoft connectivity analyzer", which had several
> steps testing deliverability of email to their domain, with the final test
> of an actual test email delivery failing.
>
> /kc

It's one of the outbound IP addresses for the Microsoft Remote Connectivity
Analyzer, as documented here:
https://support.office.com/en-gb/article/office-365-urls-and-ip-address-ranges-8548a211-3fe7-47cb-abb1-355ea5aa88a2
.

Your client's mail exchanger is rejecting the test e-mail message because
that particular outbound IP address does not have PTR resource record.
Interestingly, all of the IP addresses listed do not.

Josh