How to fix verizon.net mail sent to hotmail.com

I've had the same problem. I started corresponding regularly with a hotmail.com address in early April, and I sent several messages successfully over the next few weeks. I had a message bounce back on May 7, then another one bounced back today. I don't understand why everything was okay for a while and then it wasn't.

Here is the text of today's Failure Notice.

550: 5.7.515 Access denied, sending domain verizon.net doesn't meet the required authentication level. The sender's domain in the 5322.From address doesn't meet the authentication requirements defined for the sender. To learn how to fix this see: https://go.microsoft.com/fwlink/p/?linkid=2319303 Spf= Pass , Dkim= Fail , Dmarc= Pass

There's more, but I think the fact the rest is in all caps got my first comment deleted. I've changed the case of the domain name and Dmarc above to avoid anything else that's all caps.

Thanks for any insight you can offer.

@Bob said

sending domain verizon.net doesn't meet the required authentication level. Spf= Pass , Dkim= Fail , Dmarc= Pass

Microsoft has started to implement much tighter rules on incoming mail, including that it must pass DKIM verification.

https://techcommunity.microsoft.com/blog/microsoftdefenderforoffice365blog/strengthening-email-ecosystem-outlook%E2%80%99s-new-requirements-for-high%E2%80%90volume-senders/4399730

It's a bit hit or miss (depending on the volume of mail and other factors). That's why it seems to be an on again, off again thing for you.

I know that all verizon.net accounts have been migrated to either AOL or Yahoo. So my guess is your problem is with one of those mail providers. Something got missed during the migration?

https://www.verizon.com/support/residential/email

Our verizon.com email has been administered by AOL for years now, but this is a recent issue, so the migration seems an unlikely source of the problem. Emails to a specific hotmail addressee went through a month ago, but not over the past few days. The Microsoft link you provided refers to a policy change taking effect on May 5, 2025. The May 5 part would fit with the "before" and "after" behavior I saw, but it's off by a year. What I'd like to know is whether there's anything I can do myself to address the Dkim issue, or do I have to talk with verizon/AOL?

@Bob said

policy change taking effect on May 5, 2025. The May 5 part would fit with the "before" and "after" behavior I saw, but it's off by a year.

Sorry I wasn't clear. May 2025 was when Microsoft started imposing the new Rules on "large volume senders". That means more than 5,000 emails per day (to consumer domains like @outlook.com, @hotmail.com, @live.com) and applies to the total volume sent by a single domain.

And it seem impossible that a major mail provider like AOL didn't setup up their DKIM correctly back in 2025 and no one noticed until now. So I would have to conclude that there is at least one AOL server that has become misconfigured. And you have the misfortune of using that server when you send mail that gets bounced.

anything I can do myself to address the Dkim issue, or do I have to talk with verizon/AOL?

Based on what we know at this point, I don't see any choice except to raise the issue with AOL. Sorry. I know how famously bad AOL support is.

One test you might try is to send a Plain Text, not HTML, email (is that possible from AOL Web Mail?) with a Subject of "TEST" and an empty body. If that bounces, then that rules out anything except a DKIM fail as the problem.