"One metric that some sites evidently use is email sent to accounts that are known to be inactive, which is seen as a sign of a spammy originator. This, seemingly, is where Mozilla has run into trouble. One way to avoid this problem is to track which recipients are actually reading their email; any recipient who doesn't look at any messages for a period of time can then be unsubscribed."
Shouldn't the sites bounce those emails in a way Mozilla can detect and therefore use to prune?
Shouldn't the sites bounce those emails in a way Mozilla can detect and therefore use to prune?