On 12/23/21 3:09 PM, John McDonald via Mailman-users wrote:

I am responsible for the mailing list of a local church. Recently the church was moved to using Mailman for this. When a simple message is created and sent to the mailing list most email addresses received it correctly but those with an Outlook or Hotmail account received attachments and not the message. There are three attachments and one of them has to be opened to view the message.

Am I missing some setting?

This is possibly unrelated to Mailman, and possibly happening because Outlook.com and Hotmail are both owned by Microsoft, and both are flagging your server as a spam source.

You can verify this by checking your mail server's logs. Usually a big service like Hotmail or Gmail will embed a URL in the error message where you can go to apply to be whitelisted.

If this is the problem, you may need to take additional steps (again outside of Mailman3) to be a good email server citizen, such as adding DKIM and SPF records in your domain's DNS. Unless you have both, Microsoft or Google may block your server.

It might also be a Mailman problem, but since some subscribers do get postings, I'd start with this first.

dn