strange verifiedimportant

Whatever did not fit the other categories ends up here: unexpected responses, protocol irregularities, behaviour the engine has no name for. The vendor's description is candid — "the number of strange errors or behaviors that resulted in a not delivered email". It is excluded from failures and from allerrors alike, which means a node can be losing mail in a way nobody understands while both totals stay clean. That combination — unclassified and uncounted — makes it the most interesting counter on the list for anyone investigating a node whose numbers look fine and whose customers complain. Our own charts should include it in the failure total and label it plainly, since an unexplained failure is still a failure.