feat: pause campaign batches on SMTP failure

docs/CAMPAIGN_DELIVERY_RUNBOOK.md

@@ -62,6 +62,10 @@ Before the first live send for a sender domain or mail-server profile:
 6. If a synchronous request is used, keep Review and send open: it polls the
    durable counters while the request runs. A rejection occurs before SMTP and
    directs oversized runs to workers.
+7. Review the SMTP batch line. `ready` means DNS/connectivity/TLS/auth preflight
+   succeeded. Connection and reconnect counts explain reuse. `paused` means a
+   systemic transport failure stopped the remaining jobs before their SMTP
+   effect; test/correct the Mail profile and explicitly resume the queue.
 
 ## Outcome Handling
 
@@ -88,6 +92,9 @@ unknown provider attempt merely to repair the other layer's state.
 - `failed_temporary`: Retry explicitly after checking the error and retry count.
 - `failed_permanent`: Retry only if the operator has corrected the root cause and
   intentionally includes permanent failures.
+- `paused` after a systemic SMTP failure: do not resume until the shared Mail
+  profile passes its connection test. Authentication, sender rejection, and
+  unavailable connectivity affect the batch rather than one recipient.
 - `outcome_unknown`: Do not retry directly. Check SMTP logs, mailbox evidence, or
   provider control panels, then reconcile as accepted or not sent.
 - `claimed` or `sending` that does not progress: treat as a worker interruption.