This procedure can be used to move a imap folder between users on a server (or between servers). 

  * copy imap folder over.
  * chown all to cyrus:mail
  * make sure there's a cyrus.header file in there, (touch and chown it if not)
  * stop cyrus
  * /usr/lib/cyrus/reconstruct -rf user.newuser
  * start cyrus

  * fix ACL on new directories:
  * grab a directory listing one per line (find -type d),  create a vim script to change each line to 2 lines, and do the following: for eg:
    * dam user.newuser.copied-directory."subdirectory with spaces" olduser
    * sam user.newuser.copied-directory."subdirectory with spaces" newuser lrswipkxtecda

  * replace slashes with dots in sub/subdirectories
  * escape quote marks ' -> \'

  * paste the script into cryadm

dam = delete acl on mailbox, sam = set acl on mailbox