(setq elmo-imap4-debug t)

CF-SX2-252$ cat -n /usr/pkg/share/emacs/site-lisp/wl/elmo-imap4.el | sed  -n 500,529p
   500     (elmo-imap4-read-untagged
   501      (elmo-network-session-process-internal session))
   502     'continue-req))
   503
   504  (defun elmo-imap4-process-bye (session)
   505    (with-current-buffer (elmo-network-session-buffer session)
   506      (let ((r elmo-imap4-current-response))
   507        (setq elmo-imap4-current-response nil)
   508        (elmo-network-close-session session)
   509        (signal 'elmo-imap4-bye-error
   510                (list (concat (elmo-imap4-response-error-text r))
   511                      "Try Again")))))
   512
   513  (defun elmo-imap4-accept-continue-req (session)
   514    "Returns non-nil if `+' (continue-req) response is arrived in SESSION.
   515  If response is not `+' response, cause an error."
   516    (let (response)
   517      (setq response
   518            (elmo-imap4-read-untagged
   519             (elmo-network-session-process-internal session)))
   520      (or (elmo-imap4-response-continue-req-p response)
   521          (error "IMAP error: %s"
   522                 (or (elmo-imap4-response-error-text response)
   523                     "No continut-req from server.")))))
   524
   525  (defun elmo-imap4-read-ok (session tag)
   526    "Returns non-nil if `OK' response of the command with TAG is arrived
   527  in SESSION. If response is not `OK' response, returns nil."
   528    (elmo-imap4-response-ok-p
   529     (elmo-imap4-read-response session tag)))

*elmo-imap4264* OK arrived
[22:42:12] => ((ok nil) (status ((unseen 0) (recent 0) (messages 39))))
[22:42:12] -> mailbox size adjusted: nil, (nil)
[22:42:12] <-- elmo-imap4265 status {19}
[22:42:12] -> + OK
[22:42:12] =>((continue-req "OK"))
[22:42:12] <-- INBOX.Sent
Messages
[22:42:12] <-- (recent unseen messages)
[22:42:12] -> elmo-imap4265 NO Mailbox does not exist, or must be subscribed to.
*elmo-imap4265* NO arrived
[22:42:12] => ((no (nil "Mailbox does not exist, or must be subscribed to.")) (continue-req "OK"))
[22:42:12] -> mailbox size adjusted: nil, (nil)
[22:42:12] <-- elmo-imap4266 select {19}
[22:42:12] -> * NO Error in IMAP command received by server.
[22:42:12] =>(nil)
[22:42:13] -> + OK

Debugger entered--Lisp error: 
         (file-locked "/home/makoto/.elmo/sendlog" "makoto@CF-SX2-252 (pid 9136)")
  signal(file-locked ("/home/makoto/.elmo/sendlog" "makoto@CF-SX2-252 (pid 9136)"))
  ask-user-about-lock("/home/makoto/.elmo/sendlog" "makoto@CF-SX2-252 (pid 9136)")
  write-region(1 155 "/home/makoto/.elmo/sendlog" t no-msg nil)
  write-region-as-binary(1 155 "/home/makoto/.elmo/sendlog" t no-msg)
  wl-draft-write-sendlog(uncertain smtp "smtp.example.com" ("makoto@example.com") 
        "<yfmled6yzb8.wl-makoto@example.com>")
  wl-draft-send-mail-with-smtp()
  wl-draft-dispatch-message()
  wl-draft-normal-send-func(#<buffer +draft/1057> t)
  wl-draft-send(t)
  wl-draft-send-and-exit()
  funcall-interactively(wl-draft-send-and-exit)
  call-interactively(wl-draft-send-and-exit nil nil)
  command-execute(wl-draft-send-and-exit)