=head2 newstomail

Rewrites a news article into a mail message, using a set of newsgroup to
e-mail address mappings to determine which addresses to mail the resulting
message to.

This module does the following:  Checks to make sure there's a Newsgroups
header; drops Bcc and Resent-Bcc headers in the message; renames To, Cc,
Apparently-To, Resent-To, Resent-Cc, Return-Path, and Sender headers (if
present) to the same name prefixed by X-Original- since they may be
misinterpreted by e-mail software, and sets a new To header consisting of
the e-mail addresses corresponding to all the groups in the Newsgroups
header that have defined mappings.  Duplicate addresses are stripped out.

This module takes one configuration file directive:

=over 4

=item newstomail FILENAME

Specifies the file from which the list of newsgroup to address mappings
should be read, in the form newsgroup, whitespace, address.  If the
filename ends in .db, then the file will be assumed to be a Berkeley
database instead, with newsgroups as the keys and addresses as the values.

=back

Two failure messages are possible:

=over 4

=item Missing required Newsgroups header

The incoming message doesn't have a Newsgroups header.  This module only
handles posts and needs the Newsgroups header to determine what addresses
to which to send the message.

=item No newsgroup with a mapping

None of the newsgroups in the Newsgroups header had a mapping to an e-mail
address, so there's nowhere to send the message.

=back

This module takes no arguments.
