Paul, Are you properly rate limiting and warming up the new IPs sending volumes or just sending at normal speeds? Are you properly authenticating your email with SPF, DKIM and SPF as per the Postmaster page suggestions for sending email? Are you properly enrolled in SNDS, Junk Mail Reporting etc... More self help tips and how to contact MSFT for support can be found here: https://postmaster.live.com/pm/troubleshooting.aspx Cheers, Matt On Wed, Mar 14, 2018 at 11:34 AM, Paul Reichart <paul_reichart@wiband.com> wrote:
Wondering if anyone on the list has ever set up a mail filtering appliance or server on new IP address and had to deal with 451 messages from Office 365.
We're processing a large volume of mail and seem to be throttled by O365. Seeing something like this: 451 4.7.500 Server busy. Please try again later from [x.x.x.x]. (AS77713180) [.....outlook.com ].
We own the IP block and the address itself is not on any block lists.
It's been going on for a few days now, pissing off a lot of our customers. As expected O365's front line support is totally useless.
Any advice would be appreciated!