On Tue, Feb 27, 2018 at 11:04 AM, Ken Chase <m...@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
