212 lines
4.7 KiB
HTML
212 lines
4.7 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML
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><HEAD
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><TITLE
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>User Settings and Data</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
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REL="HOME"
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TITLE="Spam Filtering for Mail Exchangers"
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HREF="index.html"><LINK
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REL="UP"
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TITLE="Considerations"
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HREF="considerations.html"><LINK
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REL="PREVIOUS"
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TITLE="Forwarded Mail"
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HREF="forwardedmail.html"><LINK
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REL="NEXT"
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TITLE="Questions & Answers"
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HREF="qanda.html"></HEAD
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><BODY
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CLASS="section"
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#840084"
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ALINK="#0000FF"
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><DIV
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CLASS="NAVHEADER"
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><TABLE
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SUMMARY="Header navigation table"
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>Spam Filtering for Mail Exchangers: </TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="forwardedmail.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 3. Considerations</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="qanda.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="section"
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><H1
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CLASS="section"
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><A
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NAME="usersettings"
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></A
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>3.4. User Settings and Data</H1
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><P
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> There are other situations where you may want to support
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settings and data for each user at site. For instance, if you
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scan incoming mail with SpamAssassin (see <A
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HREF="datachecks.html#spamscanners"
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>Spam Scanners</A
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>), you may want to allow for individual
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spam thresholds, acceptable languages and character sets, and
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Bayesian training/data.
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</P
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><P
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> A sticking point is that SMTP-time filtering of incoming mail is
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done at the system level, before mail is being delivered to a
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particular user, and as such, does not lend itself too well to
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individual preferences. A single message may have several
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recipients; and unlike the case with <A
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HREF="forwardedmail.html"
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>Forwarded Mail</A
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>, using an aggregate of each
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recipient's preferences is not a good option. Consider a
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scenario where you have users from different linguistic
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backgrounds.
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</P
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><P
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> As it turns out, though, there is a modification to this truth.
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The trick is to limit the number of recipients in incoming
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messages to one, so that the message can be analyzed in
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accordance with the settings and data that belongs to the
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corresponding user.
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</P
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><P
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> To do this, you would accept the first <B
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CLASS="command"
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>RCPT
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TO:</B
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>, then issue a SMTP <B
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CLASS="command"
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>451</B
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> (defer)
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response to subsequent commands. If the caller is a
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well-behaved MTA, it will know how to interpret this response,
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and try later. (If it is confused, then, well, it is probably a
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sender from which you don't want to receive mail in the first
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place).
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</P
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><P
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> Obviously, this is a hack. Every mail sent to several users at
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your site will be slowed down by 30 minutes or more per
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recipient. Especially in corporate environments, where it is
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common to see e-mail discussions involving several people on the
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inside and several others on the outside, and where timelines of
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mail deliveries are essential, this is probably not a good
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solution at all.
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</P
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><P
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> Another issue that mainly pertains to corporate enterprises and
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other large sites is that incoming mail is often forwarded to
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internal machines for delivery, and that recipients don't
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normally have accounts on the mail exchanger. It may still be
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possible to support user-specific settings and data in these
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situations (e.g. via database lookups or LDAP queries), but you
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may also want to consider whether it's worth the effort.
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</P
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><P
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> That said, if you are on a small site, and where you are not
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afraid of delayed deliveries, this may be an acceptable way
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to allow each user to fine tune their filtering criteria.
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</P
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></DIV
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><DIV
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CLASS="NAVFOOTER"
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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SUMMARY="Footer navigation table"
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><A
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HREF="forwardedmail.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="index.html"
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ACCESSKEY="H"
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>Home</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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><A
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HREF="qanda.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TR
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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>Forwarded Mail</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="considerations.html"
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ACCESSKEY="U"
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>Up</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>Questions & Answers</TD
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></TR
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></TABLE
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></DIV
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></BODY
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></HTML
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> |