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<UL>
<LI><A NAME="tex2html1466"
HREF="node24.html#SECTION002410000000000000000">23.1 VERP</A>
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<H1><A NAME="SECTION002400000000000000000">
23. Bounce management</A>
</H1>
<P>
<I>Sympa</I> allows bounce (non-delivery report) management. This
prevents list owners from receiving each bounce (1 per message
sent to a bouncing subscriber) in their own mailbox. Without
automatic processing of bounces, list owners either go
mad, or just delete them without further attention.
<P>
Bounces are received at mylist-owner address (note that the -owner
suffix can be customized, see <A HREF="node8.html#kw-return-path-suffix">7.8.4</A>,
page <A HREF="node8.html#kw-return-path-suffix"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>), which should
be sent to the <A NAME="11607"></A><TT>bouncequeue</TT> program via aliases :
<P><PRE>
\samplelist-owner: "|/home/sympa/bin/bouncequeue \samplelist"
</PRE>
<P>
<A NAME="11610"></A><TT>bouncequeue</TT> (see <A HREF="node3.html#binaries">2.2</A>, page <A HREF="node3.html#binaries"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>) stores bounces in a
<A NAME="11613"></A><TT>/home/sympa/spool/bounce/</TT> spool.
<P>
Bounces are then processed by the <A NAME="11616"></A><TT>bounced.pl</TT> daemon.
This daemon analyses bounces to find out which
e-mail addresses are concerned and what kind of error was generated.
If bouncing addresses match a subscriber's address, information
is stored in the <I>Sympa</I> database (in subscriber_table). Moreover, the most recent
bounce itself is archived in <A NAME="11620"></A><TT>bounce_path/mylist/email</TT>
(where bounce_path is defined in a <A NAME="11623"></A><TT>wwsympa.conf</TT> parameter and
email is the user e-mail address).
<P>
When reviewing a list, bouncing addresses are tagged as bouncing.
You may access further information such as dates of first and last bounces,
number of received bounces for the address, the last bounce itself.
<P>
With these informations, the automatic bounce management is possible:
<P>
<UL>
<LI>The automatic task <A NAME="11626"></A><TT>eval_bouncer</TT> gives a score foreach bouncing user.
The score, between 0 to 100, allows the classification of bouncing users in two levels.
(Level 1 or 2).
According to the level, automatic actions are executed periodicaly by <A NAME="11629"></A><TT>process_bouncers</TT>
task.
<P>
</LI>
<LI>The score evaluation main parameters are:
<P>
<A NAME="11632"></A><TT>Bounces count</TT>: The number of bouncing messages received by sympa for the user.
<P>
<A NAME="11635"></A><TT>Type rate</TT> : Bounces are classified depending on the type of errors generated on the user
side. If the error type is "mailbox is full" (ie a temporary 4.2.2 error type) the type rate will be
0.5 whereas permanent errors (5.x.x) have a type rate equal to 1.
<P>
<A NAME="11638"></A><TT>Regularity rate</TT> : This rate tells if the bounces where received regularly, compared to list
traffic. The list traffic is deduced from <A NAME="11641"></A><TT>msg_count</TT> file data.
<P><PRE>
The score formula is :
Score = bounce_count * type_rate * regularity_rate
</PRE>
<P>
To avoid making decisions (ie defining a score) without enough relevant data, the score is not
evaluated if :
<P>
<UL>
<LI>The number of the number of received bounces is lower than <A NAME="11644"></A><TT>minimum_bouncing_count</TT>
(see <A HREF="node8.html#kw-minimum-bouncing-count">7.8.9</A>, page <A HREF="node8.html#kw-minimum-bouncing-count"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>)
<P>
</LI>
<LI>The bouncing period is shorter than <A NAME="11647"></A><TT>minimum_bouncing_period</TT>
(see <A HREF="node8.html#kw-minimum-bouncing-period">7.8.10</A>, page <A HREF="node8.html#kw-minimum-bouncing-period"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>)
<P>
</LI>
</UL>
<P>
</LI>
<LI>You can define the limit between each level via the <B>List configuration pannel</B>,
in subsection <B>Bounce settings</B>. (see <A HREF="node21.html#rate">20.5.2</A>) The principle consists in
associating a score interval with a level.
<P>
</LI>
<LI>You can also define wich action must be applied on each category of user.(see <A HREF="node21.html#action">20.5.2</A>)
Each time an action will be done, a notification email will be send to the person of your choice.
(see <A HREF="node21.html#notification">20.5.2</A>)
<P>
</LI>
</UL>
<P>
<H1><A NAME="SECTION002410000000000000000"></A>
<A NAME="verp"></A>
<BR>
23.1 VERP
</H1>
<P>
VERP (Variable Envelop Return Path) is used to ease automatic recognition of
subscribers email address when receiving a bounce. If VERP is enabled, the subscriber address is encoded
in the return path itself so Sympa bounce management processus (bounced) will use the address the bounce
was received for to retreive the subscriber email. This is very usefull because sometimes, non delivery
report don't contain the initial subscriber email address but an alternative address where messages
are forwarded. VERP is the only solution to detect automaticaly these subscriber errors but the cost
of VERP is significant, indeed VERP requires to distribute a separate message for each subscriber and
break the bulk emailer grouping optimization.
<P>
In order to benefit from VERP and keep distribution process fast, Sympa enables VERP only for a share
of the list members. If texttt <A NAME="11650"></A><TT>verp_rate</TT> (see <A HREF="node8.html#kw-verp-rate">7.8.1</A>,page <A HREF="node8.html#kw-verp-rate"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="crossref.png"></A>) is 10% then after 10 messages distributed in the list
all subscribers have received at least one message where VERP was enabled. Later distribution message enable
VERP also for all users where some bounce wer collected and analysed by previous VERP mechanism.
<P>
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