Thanks. Looking at one of the notifications, I see this is a DKIM failure.: The response from the remote server was:
550 5.7.9 This mail has been blocked because the sender is unauthenticated. Yahoo requires all senders to authenticate with either SPF or DKIM. Authentication results: DKIM = FAILURE - SPF XXX.org with ip X.Y.Z.W = SUCCESS. See https://senders.yahooinc.com/smtp-error-codes/#authentication-failures for more information. This has worked for a long time. What would suddenly cause DKIM failures?
On Thu, May 7, 2026 at 11:02 AM Paul Tomblin via Mailman-users < mailman-users@mailman3.org> wrote:
The first thing I’d do is look at the outgoing mail logs. If it’s bouncing 1/3rd of your users, it’s very likely it’s one or two whole domains that are bouncing, probably because your IP has been black listed or you don’t have DKIM set up right or something like that. The outgoing mail logs might tell you that. Also, don’t you get a copy of the “disabling bounce”? I always get one of that when somebody gets bounced off the list. The bounce message itself usually gives you a clue as well - I think it’s in an attachment called email.eml or something like that.
On Thu, May 7, 2026, at 10:39 AM, Stephen Daniel wrote:
Colleagues --
I run a small mailman3 server with perhaps 10 lists. All the lists are small.
Over the past two days about a third of the users in my most active list have been disabled by bounces. I assume the problem is with my setup, not with all of those users.
How do I debug this? Can I see the text of any of the bounce messages to understand why the emails bounced?
This issue might stem from my running somewhat old software. Currently running mailman 3.3.5.
Thanks!
-- Stephen Daniel
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