On Oct 25, 2021, at 2:23 PM, Joseph Tam jtam.home@gmail.com wrote:
On Mon, 25 Oct 2021, Ron Garret wrote:
Note that message-ids are not guaranteed to be unique. During my test I found groups of as many as 20 different messages with the same message ID. (Turns out this makes quite a reliable spam signal!)
It's by far not a rare situation: duplicate message-ids happen whenever the sender names more than one local recipient during SMTP. It's a wholly unreliable way to indicates spaminess. However, if a high proportion of those recipients do not exist, ...
I think you may have misunderstood. What you say isn’t wrong, but in the case of multiple local SMTP recipients, all of the duplicate messages will have the same content. What I have found is the same message ID in messages with (very) *different* content (and often sent to the same user). All of that has been spam (and it is hard to imagine any situation in which it would not be).
rg