o365
Bounce message. SMTP rejection. Deferral message. Non-delivery report (NDR). 5xx error. 4xx error. No matter what you call them, there are a zillion different kinds of them out there. Heck, Microsoft’s got at least four different ways to tell you “user unknown.” Memorizing all of these is hard. Probably impossible. So, if you’re looking for a big ole’ list of all (or at least most) of the different rejections or deferrals you can run into when sending emails to Microsoft, let’s be grateful that they’ve got a very handy chart that breaks down just about all of the different types of 4xx and 5xx responses you can receive when trying to send to Exchange Online / Office 365. There are close to 70 different types of NDRs listed; and it’s a good and handy resource that you should bookmark, though I admit that I don’t know if it covers absolutely
Today, Wednesday, October 11th, many senders are reporting trouble (specifically, delayed mail) when attempting to send email to Microsoft-hosted subscribers. Here’s more on the issue from Steve Atkins from Word to the Wise. I’m keeping a close eye on my Office365 admin dashboard to watch for updates on this issue. Microsoft has logged this as “incident EX680695” and those with O365 admin access can go to Home -> Health -> Exchange Online -> Health to see the current status and click on the incident/advisories there to find the latest details. Here’s a direct link to that incident information, which likely only works if you have appropriate access.Many (but not all) senders were impacted, seeing “451 4.7.500 Server busy” delivery delays when sending to email domains hosted by Office 365 / Exchange Online. Many of the senders reporting trouble were located in the EU; suggesting that the issue may be EU-specific, or specific