Useful tips for configuration options.

If you have many subscribers from certain online services, you can somewhat
reduce average delivery time by ensuring that hosts which house many
addresses get their own batches.  You can do this using 'minseparate',
which tells TLB how many addresses a single host must have before it gets
its own batch.  Addresses on other hosts are collected into batches of
'maxdomains' size, 10 addresses by default.


If you have many addresses in far-off lands, or just very many addresses in
general, it may help to have one or more remote exploders.  These are
remote sites which have agreed to deliver a portion of your mail to you.
To set up a remote exploder, first ask the postmaster at the remote site to
make the necessary configuration changes.  This is important; few sites
will be pleased if you try to route mail through them without obtaining
permission.  At best it won't work; at worst you will be breaking the
computer access laws of multiple countries.

Next devise a host entry for the exploder, something like:

%nordland = ('hostname' => 'arctic.air.no');

Then decide which addresses that site will deliver.  Cook up a regular
expression which matches these addresses, then construct a destination like
the following, and place it in the delivery_matrix before the default list
(destinations are compared in order).

{
 'regexp'      => '(no|se|fi)$',
 'hosts'       => [ \%nordland, ],
 'numbatches'  => 10, # They prefer that we limit the
                      # load to ten simultaneous
                      # processes
}

You should be sure to ask the remote site what kind of load they will
accept from you; they may want only a single batch per message (equivalent
to 'numbatches' => 1).  Once you've set this up, run a test:

tlb -t your@address -d56 (options) your.config

replacing (options) with the options necessary for your config file, and
eliminating the -d56 if you don't want such verbose output.  This will send
a mail to you through each of the hosts you have defined, to make sure that
they will deliver mail for you.


If you have several hosts capable of doing outbound mail delivery, you can
spread the load around and/or use smaller batches to speed delivery.  To do
so, make host entries for each host which will deliver mail, like the
following:

%host1 = ('hostname' => 'mailhost1.my.dom');
%host2 = ('hostname' => 'mailhost2.my.dom');
etc.

Then list the host entries in the 'hosts' field of the destination:

 'hosts' => [ \%host1, \%host2 ],

The load will be automatically distributed evenly between the hosts you
list.  You can list a host more than once, and it will receive more of the
load.