Comment 33 for bug 885525

Changing this bug back to "Gmail IMAP only issue".
Problem is due to Tb's particularity for Gmail IMAP.
  [Gmail]/Trash is always used as trash folder, regardless of trash folder
  selection at Server Settings.
Next Gmail's/Gmail IMAP's particularity is relevant to observed phenomenon,
  When a mail is copied to [Gmail]/Trash, any Gmail Label is removed from the
  mail including [Gmail]/All Mail by Gmail/Gmail IMAP
but it's irrelevant to problem of comment #0 itself.
Original problem reported to comment #0 of this bug by bug opener is "trash folder selection at Server Settings is ignored by Tb if Gmail IMAP".

To all proble reporters in this bug for other than Gmail IMAP:

If problem just after trash folder selection change at Server Setting, and if problem while icon for newly selected trash folder is not changed to "Trash Can" icon, read bug 631362, and check whether your problem is same as bug 631362 or not.
If different from bug 631362 and not Gmail IMAP, get IMAP log and check IMAP level flow by yourself, and search bugzilla.mozilla.org well for already reported problem via "Advanced Search" of B.M.O, and, if not found, open separate bug for your problem with attaching log file(never paste), please.

Please note that same external symptom of "trash folder selection at Server Settings doesn't work" is not always same problem.
There are at least several kinds of problem which produces the same external symptom.
(1) This bug, for problem of comment #0, Gmail's particularity relevant problem. Phenomenon of comment #0 is easiliy be reproduced.
(2) bug 631362 (if Gmail IMAP, bug 631362 is irrelevant)
(3) Problem due to localized trash folder name by localized Tb.
    Because localized Tb puts localized trash folder name in prefs.js setting
    of mail.server.serverN.trash_folder_name, it causes mismatch between
    real folder name at IMAP server.
(4) Problem due to namespace.
    Because Tb puts <namespace>/trash-foler-name in prefs.js setting
    of mail.server.serverN.trash_folder_name,
    it causes mismatch between expectation by folder acceess component who
    expects string without namespae in mail.server.serverN.trash_folder_name,
    and <namespace>/<namespace>/trash-foler-name is used as trash folder.
(5) Other than above (1) to (4).

Please keep this bug for problem of above (1) only, for original comment #0 of this bug only.