Seen this recently? 451 Message temporarily deferred due to unresolvable RFC.5321 from domain; see This is Yahoo doing some extra work to identify that the 5321.From domain1The return-path, aka the 821.From, 5321.From, or bounce address is the email address you send from at the protocol level, not the email address in the From: header, and it’s the address any bounces will be sent to. of...
Message not compliant with the RFCs
Every once in a while we’ll see a rejection from Yahoo that says RFCs 554 5.0.0 Message not accepted due to failed RFC compliance. What does that mean and what can we do about it? It really does mean exactly what it says on the label: there’s something about the message that is not in compliance with any number of RFCs and are not going to accept the message in its current state. When...
Yahoo having problems
Yahoo seems to be having some massive system issues the last 24 hours or so. DNS has been down, mail was down. I’m seeing reports things are coming back now, but there’s a lot of backed up mail traffic and the congestion may take a few hours to resolve. If you have the ability to do traffic shaping on the sending end, now would be a good time to be extra conservative in your sending...
Dead addresses tell us things
There was confirmation this week that the increase in “user unknown” messages from Yahoo is actually Yahoo cleaning out abandoned accounts. At the same time a Yahoo is sending out notifications to folks to log into mail. The first thing every sender should do is remove all these Yahoo addresses from their lists. They’re done, kaput. Gone. There are some other things worth doing...
Email news today
Ironport have rolled out an update to their rule engine which has a bug causing mail problems. According to discussion on the mailop list, the new rule engine is folding the header with a line feed (LF) rather than a carriage return (CRLF). This is breaking things, including DKIM signatures. Ironport is aware of the issue. I expect an updated rollout shortly. AOL migrated the last few users onto...
Verizon Media Postmaster Site
Marcel brought up in the comments that Verizon Media has a postmaster site. The ex-AOL and Yahoo folks have done a great job providing information for senders to help troubleshoot their mail. There is a direct link to receive sender support. As I’ve said before, you should always use the form when looking for sender support. Thanks to all the VM folks who have worked so hard to get a new...
Whitelisting is dead
A decade or so ago I was offering whitelisting services to clients. It was pretty simple. I’d collect a bunch of information and do an audit on the customer’s sending. They’d get a report back identifying any issues that would limit their chances at acceptance. Then I’d go and fill in the forms on behalf of the client. Simple enough work, and it made clients feel better...
OATH and Microsoft updates
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...
Affiliate marketing overview
Most retailers have realized that sending unsolicited email is bad for their overall deliverability. Still, the idea they can send mail to people who never heard of them is seductive. Enter affiliate email. That magical place where companies hire an agency, or a contractor, or some other third party to send email advertising their new product. Their mail and company reputation is protected...
What kind of mail do filters target?
All to often we think of filters as a linear scale. There’s blocking on one end, and there’s an inbox on the other. Every email falls somewhere on that line. Makes sense, right? Bad mail is blocked, good mail goes to the inbox. The bulk folder exists for mail that’s not bad enough to block, but isn’t good enough to go to the inbox. Once we get to that model, we can think...