If you’re seeing a lot of “451 4.7.500 Server busy. Please try again later” from Office365 this morning you’re not alone. Microsoft are aware of the issue, and incident EX680695 says: Current status: We’ve identified that specific IP addresses are being unexpectedly limited by our anti-spam procedures, causing inbound external email delivery to become throttled and delayed...
It looks like Microsoft are getting pickier about email address syntax, rejecting mail that uses illegal address formats. That might be what’s causing that “550 5.6.0 CAT.InvalidContent.Exception: DataSourceOperationException, proxyAddress: prefix not supported – ; cannot handle content of message” rejection. Why do we care? It’s good to send syntactically valid...
This is a followup from a post a few weeks ago about authentication changes at Office365. We have some more clarity on what is going on there. This is all best information we have right now. Microsoft is now requiring authentication to match the visible from address in order to reach the inbox at Office365. That means, either the SPF domain or the DKIM domain must align (in the DMARC sense) to...
Many deliverability folks stopped recommending publishing SPF records for the 5322.from address to get delivery to Microsoft. I even remember Microsoft saying they were stopping doing SenderID style checking. A discussion on the emailgeeks slack channel has me rethinking that. It started out with one participant asking if other folks were seeing delivery improvement at MS if they added a SPF...
A question came up on the email geeks slack channel (Join Here) about SenderID. They recently had a customer ask for SenderID authentication. We’ve written about it a few times: (Hotmail moves to SPF Authentication and Until it stops moving) but we’ve not actually stated the reasons why in a post. SenderID was basically SPF version 2. It tried to use the same mechanism as SPF to...
One of the big topics of discussion in various deliverability circles is the problems many places are seeing with delivery to Microsoft properties. One of the challenges is that Microsoft seems to be happy with how their filters are working, while senders are seeing vastly different data. I started thinking about reporting, how we generate reports and how do we know the reports are correct...
An on the ball reader sent me a note today showing a bounce message indicating microsoft was rejecting mail due to a Spamhaus Blocklist Listing. 5.7.1 Client host [10.10.10.10] blocked using Spamhaus. To request removal from this list see (S3130). [VE1EUR03FT043.eop-EUR03.prod.protection.outlook.com] The IP in question is listed on the CSS, which means at a minimum Microsoft is using the SBL. I...
A c/p from an email I sent to a mailing list. I think we’re seeing a new normal, or are still on the pathway to a new normal. Here’s my theory. 1) Hotmail made a lot of underlying code changes, learning from 2 decades of spam filtering. They had a chance to write a new codebase and they took it. 2) The changes had some interesting effects that they couldn’t test for and didn’t expect. They spent...
I’ve seen multiple people asking questions about what’s going to happen with the Yahoo and AOL FBLs after the transition to the new Oath infrastructure. The most current information we have says that the AOL FBL (IP based) is going away. This FBL is handled by the AOL infrastructure. As AOL users are moved to the new infrastructure any complaints based on their actions will come...
Dear Laura, I sometimes get in arguments with clients where I say, “your open rate is 3%, you need to do some list pruning” and they say, “my recipient list is 100% b2b, and b2b filters don’t care about engagement, so it doesn’t matter if my list is really old and unengaged.” This is wrong in cases where the business is using Outlook or Gsuite, both of which are going to care if they see...
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