This is already fixed for lists that are managed by Launchpad AIUI. We need an interrogative protocol for external lists to (e.g. - to sketch one, a link in the mail you can click on if you get it twice, set on mails to non-lp-managed team contact addresses) to solve it for other sorts of mail-expanders.
Alternatively, perhaps we could lie slightly and set the same msg ID for all our messages even though they are different; that way if you're subscribed to two lists and your mail client does msg-de-duping (which many providers do) you'd only see one.
This is already fixed for lists that are managed by Launchpad AIUI. We need an interrogative protocol for external lists to (e.g. - to sketch one, a link in the mail you can click on if you get it twice, set on mails to non-lp-managed team contact addresses) to solve it for other sorts of mail-expanders.
Alternatively, perhaps we could lie slightly and set the same msg ID for all our messages even though they are different; that way if you're subscribed to two lists and your mail client does msg-de-duping (which many providers do) you'd only see one.