(smtp-send-command process
(format
(if smtp-notify-success
- "RCPT TO:<%s> NOTIFY=SUCCESS"
+ (if (memq 'dsn extensions)
+ "RCPT TO:<%s> NOTIFY=SUCCESS"
+ (throw 'done
+ (format "Delivery Status Notifications is not available")))
"RCPT TO:<%s>")
(car recipients)))
(setq recipients (cdr recipients))