Expiration does not work + solution

[Trung Tran-Duc <trung.tranduc@prague.ixos.cz>]

I am using Pgnus 0.80 + nnimap 0.94 + M$ Exchange 5.5.
My nnmail-expiry-wait is set to 7 days (the default)
Expiration does not work. This is from *imap-log*

....
35 UID SEARCH UID 2:14,17:18,21:26 NOT SINCE 16-Mar-99
35 BAD .....
...

The obvious reason is nnimap uses two-digit years in the NOT SINCE search
clause and the IMAP server does not like it. The fix is really simple and I
think it should not break other IMAP servers

--8<--
;;
;; from nnimap.el
;;

(defun nnimap-date-days-ago (daysago)
  "Return date, in format \"3-Aug-98\", for DAYSAGO days ago."

  ;; 1999-03-23  Trung Tran-Duc <trung.tranduc@prague.ixos.cz>
  ;; 3-Aug-98 is bad, MS Exchange refuses to take this date
  ;; should be 3-Aug-1998
  (let ((date (format-time-string "%d-%b-%Y" ;was "%d-%b-%y" 
				  (nnimap-time-substract
				   (current-time)
				   (if (fboundp 'days-to-time)
				       (days-to-time daysago)
				     (nnmail-days-to-time daysago))))))
    (if (eq ?0 (string-to-char date))
	(substring date 1)
      date)))
--8<--

In *imap-log* I also see
...
37 UID STORE 2:14 -FLAGS (gnus-expire)
37 BAD protocol error: "Invalid flags set for STORE command"
...

It looks like nnimap tries to store a user-defined flag and the server refuses
to obey. Does nnimap gracefully fall back in this case?

-trung