On Sep 8, 2026, at 9:26 a, Washington Odhiambo <[email protected]> wrote:

I have some clients using them so this interests me.

You should be happy you have no issues! Don’t tempt fate.

Can you please share the content of the NDRs from your bounces - both from the 
ML and the personal email you sent to them? Of course obfuscate whatever you 
consider sensible.

I spoke too soon without double-checking - 
mailmanlists.net<http://mailmanlists.net> does not have their email hosted with 
MS 365 - they use migadu.com.

Bounce from my email to 
[email protected]<mailto:[email protected]>:


Delivery has failed to these recipients or groups:

[email protected] 
([email protected])<mailto:[email protected]>
Your message wasn't delivered. Despite repeated attempts to deliver your 
message, a connection to the remote server couldn't be made.

Contact the recipient by some other means (by phone, for example) and ask them 
to tell their email admin that it appears that your email system is unable to 
connecto their email system. Give them the error details shown below. It's 
likely that the recipient's email admin is the only one who can fix this 
problem.

For more information and tips to fix this issue see this article: 
https://go.microsoft.com/fwlink/?LinkId=389361.



Diagnostic information for administrators:

Generating server: 
MW4PR12MB8611.namprd12.prod.outlook.com<http://mw4pr12mb8611.namprd12.prod.outlook.com/>
Receiving server: 
MW4PR12MB8611.namprd12.prod.outlook.com<http://mw4pr12mb8611.namprd12.prod.outlook.com/>

[email protected]<mailto:[email protected]>
9/8/2026 4:31:59 AM - Server at 
MW4PR12MB8611.namprd12.prod.outlook.com<http://mw4pr12mb8611.namprd12.prod.outlook.com/>
 returned '550 5.4.317 Message expired, cannot connect to remote server(451 
4.4.8 MX hosts of 'mailmanlists.net<http://mailmanlists.net/>' failed MTA-STS 
validation.)'
9/8/2026 4:21:59 AM - Server at mailmanlists.net<http://mailmanlists.net/> 
(0.0.0.0) returned '450 4.4.317 Cannot establish session with remote server 
[Message=451 4.4.8 MX hosts of 'mailmanlists.net<http://mailmanlists.net/>' 
failed MTA-STS validation.] 
[LastAttemptedServerName=mailmanlists.net<http://mailmanlists.net/>] 
[BL6PEPF0001E442.namprd02.prod.outlook.com<http://bl6pepf0001e442.namprd02.prod.outlook.com/>
 2026-09-08T04:21:59.309Z 08DF0B0055FEBFFE](451 4.4.8 MX hosts of 
'mailmanlists.net<http://mailmanlists.net/>' failed MTA-STS validation.)'




Did something change in your DNS settings recently?

No.

-Brie


__
Best regards,
Odhiambo WASHINGTON,
Nairobi,KE
+254 7 3200 0004/+254 7 2274 3223
 In an Internet failure case, the #1 suspect is a constant: DNS.
"Oh, the cruft.", egrep -v '^$|^.*#' ¯\_(ツ)_/¯ :-)
[How to ask smart questions: http://www.catb.org/~esr/faqs/smart-questions.html]

On Tue, Sep 8, 2026, 14:40 Brie Yoder via Mailman-Users 
<[email protected]<mailto:[email protected]>> wrote:
I am one of those who had been hosting email lists with Dreamhost, who moved 
over to mailmanlists.net<http://mailmanlists.net/> <http://mailmanlists.net/>. 
The experience has been mostly very good - they have been very responsive and 
helpful.

However, in a recent spate of bounces from Apple domains (e.g. 
mac.com<http://mac.com/> <http://mac.com/>, icloud.com<http://icloud.com/>) and 
MS domains (e.g. msn.com<http://msn.com/> <http://msn.com/>, 
live.com<http://live.com/> <http://live.com/>) I have been trying to contact 
[email protected]<mailto:[email protected]> 
<mailto:[email protected]<mailto:[email protected]>> for help and 
now emails to THEM are bouncing - they are hosted with MS 365.

Is anyone from mailmanlists.net<http://mailmanlists.net/> 
<http://mailmanlists.net/> on this list? I guess I will need to call them in 
Australia ugh…

-Brie

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