Log Message:
Update to 0.51. From the changelog:

* Messages in the pending directory are no longer deleted after they
  are confirmed (or released) and delivered.  Now they are simply
  noted in the DELIVERED_CACHE file.

* BOUNCE_TEXT_ALREADY_CONFIRMED has been deprecated.

* The confirm_accept.txt template has been modified.  The message body
  of the notification is no longer hardcoded, but rather stored in
  %(confirm_accept_text)s, which comes from one of the following
  tmdarc variables depending on context:

  CONFIRM_ACCEPT_TEXT_INITIAL
  CONFIRM_ACCEPT_TEXT_ALREADY_CONFIRMED
  CONFIRM_ACCEPT_TEXT_ALREADY_RELEASED

* Custom templates are now referred to by a template directory rather
  than individually.  Any templates found in this directory will be
  used, otherwise the default templates will be used.  You can specify
  a custom template directory in one of two ways:

  A TEMPLATE_DIR setting in your tmdarc.  This replaces use of
  CONFIRM_ACCEPT_TEMPLATE and CONFIRM_REQUEST_TEMPLATE.

  tmda-filter's -t option, which replaces both -A and -R.

* The 'unquoted' and 'parens' options to MESSAGE_FROM_STYLE have been
  deprecated.  'angles' now double-quotes the fullname only when
  necessary.