Controls the characters used by the "%r" indicator in `` $status_format''. The first character is used when the mailbox is unchanged. The second is used when the mailbox has been changed, and it needs to be resynchronized. The third is used if the mailbox is in read-only mode, or if the mailbox will not be written when exiting that mailbox (You can toggle whether to write changes to a mailbox with the toggle-write operation, bound by default to "%"). The fourth is used to indicate that the current folder has been opened in attach- message mode (Certain operations like composing a new mail, replying, forwarding, etc. are not permitted in this mode).