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\documentclass[a4paper]{article}

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  \def\UrlLeft{<}%
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\author{
  Tony~Finch \email{fanf2@cam.ac.uk}\\
  Mail Support\\
  University of Cambridge Computing Service\\
}

\title{
  Email emergency broadcast
}

\date{
  August 2009
  \footnote{
    \texttt{
      $\$$Cambridge: hermes/doc/misc/emergency-broadcast.tex,v 1.16 2009/08/13 14:37:45 fanf2 Exp $\$$
    }
  }
}

\begin{document}

\maketitle

%

\section{Requirements}

\begin{itemize}

\item Send email to all \atcam\ email addresses.

\item Use of the facility is controlled by a password in the
  \hdr{Subject} line of the message.

\item The message will also be displayed on the Hermes Webmail login page.

\item No action is required by the email system managers.

\item As simple as possible, to minimise the chance of problems during
  an emergency.

\end{itemize}

\begin{note}
  This is a draft. In particular, the details of liaison between the
  Computing Service and staff responsible for emergency broadcast are
  still to be determined. See section \ref{TBD}.
\end{note}

%

\section{Sending an emergency broadcast message}

To use the email emergency broadcast system, send a message to
\email{ucam-emergency-broadcast@lists.cam.ac.uk}. You must use an
email address at \camacuk\ or at any subdomain of \camacuk.

The \hdr{Subject} line of your message must start with the password in
square brackets. The password must match exactly; upper case
``\texttt{A}'' is considered different from lower case ``\texttt{a}''.
The following example does not include the real password.

\begin{verbatim}
  Subject: [PassWord] evacuate West Cambridge site
\end{verbatim}

\begin{note}
  The message will be broadcast to all \atcam\ addresses without human
  intervention. There is \emph{no} moderation step, and there are
  \emph{no} restrictions on who can send a broadcast message, except
  they must use a valid \camacuk\ email address and include the
  correct password in the subject line.
\end{note}

%

\section{Sending a test message}

There is a facility for testing all the internal mechanisms of the
emergency broadcast system, except for sending the message to all
\atcam\ addresses and updating the Hermes Webmail login page. To use
it, send a message to \email{ucam-test-broadcast@lists.cam.ac.uk} with
a password in the \hdr{Subject} line as described in the previous
section.

A test message causes two messages to be sent to the
\email{ucam-broadcasters@lists.cam.ac.uk} mailing list. It modified as
described in section \ref{mangle} then delivered to the list instead
of to all \atcam\ addresses. It is further stripped as described in
section \ref{webmail} then sent to the list as a second message
instead of being inserted into the webmail login page.

%

\section{Disseminating the password}
\label{TBD}

\begin{note}
  Details in this section have not been finalized.
\end{note}

The mailing list \email{ucam-broadcasters@lists.cam.ac.uk}
is also intended for liaison between the Computing Service and staff
who are responsible for emergency communications, as well as receiving
test messages as described in the previous section.

At the moment membership of the list is managed by Computing Service
staff. This should be delegated to people more directly responsible
for emergency communications.

We suggest that the password is updated on a regular schedule. The
mailing list should not be directly used to transmit the password, but
it can be used to inform the appropriate people that a new password
will be conveyed by other means. The password can only be changed by
the email system managers.

%

\section{How messages are altered before broadcast}
\label{mangle}

The body of a message is not changed. Emergency broadcast messages
should be short and should not use fancy formatting or attachments.
Senders should take care that they use a suitable signature block.

\begin{note}
  There are \emph{no} technical mechanisms to enforce these
  posting guidelines. This is in order to keep the mechanisms as
  simple as possible.
\end{note}

A number of changes are made to the message headers.

The password is deleted from the \hdr{Subject} line, and
``{\sf [ EMERGENCY BROADCAST ]}'' is appended. This tag is added to
the end so that as much of the substantive text as possible appears in
recipients' inbox listings. After processing the example looks like:

\begin{verbatim}
  Subject: evacuate West Cambridge site  [ EMERGENCY BROADCAST ]
\end{verbatim}

All address lines are deleted (\hdr{Sender}, \hdr{From}, \hdr{To},
\hdr{CC}, \hdr{BCC}, \hdr{Reply-To}) to be replaced by the following
lines. The \hdr{From} line is designed so that ``{\sf EMERGENCY
 BROADCAST}'' will appear in recipients' inbox listings.

\begin{verbatim}
  From: EMERGENCY BROADCAST <ucam-emergency-broadcast-do-not-reply@lists.cam.ac.uk>
  To: University of Cambridge Emergency Broadcast :;
\end{verbatim}

%

\section{Updating the Hermes Webmail login page}
\label{webmail}

Every five minutes an automated task checks for emergency broadcast
messages and updates the Hermes Webmail login page if necessary. All
recent emergency broadcast messages are displayed on the login page,
most recent first (the same order as a blog). Messages can only be
erased by the email system managers.

Substantial changes are made to the broadcast message. The email
headers other than \hdr{Subject} and \hdr{Date} are stripped off and
any fancy formatting is removed. Stripping the message avoids any
unwanted interactions between webmail's HTML and any HTML in the
broadcast message. Similar changes are not made by the main broadcast
mechanism to keep the more important functionality simpler.

%

\section{Handling unwanted messages}

Messages sent to \email{ucam-emergency-broadcast@lists.cam.ac.uk} or
\email{ucam-test-broadcast@lists.cam.ac.uk} from a
non-\camacuk\ address and/or without the correct password are rejected
with an error message saying ``{\sf Authorization check failed}''.

Replies to broadcast messages are rejected with an error message
saying ``{\sf Please do not reply to broadcast messages}''.
Out-of-office auto-replies and delivery failure notifications are
discarded.

%

\end{document}

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