[Mailman-Users] Strange Wiki entry for Postfix Tuning

Stefan Förster cite+mailman-users at incertum.net
Wed Aug 5 12:23:46 CEST 2009

* Ralf Hildebrandt <Ralf.Hildebrandt at charite.de>:
> * Stefan Förster <cite+mailman-users at incertum.net>:
> > | smtp_mx_session_limit (default: 2)
> > 
> > While I can certainly imagine larger sites having somewhere between
> > five to ten MXs, 100 seems a bit... oversized.
> maybe it tries to set a very hight threshold, thus ALWAYS using ALL
> MXes?

You don't have an infinite amount of smtp(8) delivery agents, and you
don't want to keep them all busy trying the 14th MX of a destination
which is most probably dead.

What you actually want to do is ensure that you try at least

floor($num_mx / 2) + 1

different hosts (hello, greylisting!). Mailman can help you in solving

list_lists | awk '(NR > 1){print $1}' | \
    while read list; do
        list_members $list
   done | cut -d@ -f2 | sort -u  > /tmp/domains

num_mx=0; while read domain; do
    num_tmp=$(dig $domain mx +short | wc -l)
    if [ $num_tmp -gt $num_mx ]; then
done < /tmp/domains
echo "Maximum number of MX entries: $num_mx"
echo "smtp_mx_session_limit should be: $((num_mx/2+1))"

In my case, this script returns "7", so smtp_mx_session_limit should
be "4". The problem with this script is, however, that it relies on
"list_lists" and "list_members" being available to a user with shell

I'm running a Debian package of Mailman and I know that it is
modified, I just don't know to which extent. Perhaps someone with more
knowledge could comment on the availability of those two helper
commands in a standard Mailman installation? Perhaps they must be
executed as the Mailman user, or with some special environment.


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