A package TPmail is allowed to use various schemes to work.
Let's take a look to the typical schemes to use of the package.
Use together TPmail+sendmail on the external mail server accepting all incoming mail.
It is a very happy case because it is possible to use all posssibilities of
the packages without any limitations. If this server is the transit server and you
don't want to filter mail here but you may enable the messages marks by the
anti-spam filter and really filter on the other server.
Use together TPmail+sendmail on the transit (intermediate) mail server
accepting all transit mail also incoming outside. In this case
it is possible to use only partially the package's possibilities. Standard
anti-spam module cannot be used in this case because it is required to be first
in a chain accepting all incoming external mail (module must be present on
the first accepting mail server). But for the organizations that will be used
a such scheme there is possible to use the TPmail with the module test_lmta.
A given module even if it don't have a direct interaction with a server-sender
can be marked the messages (spam or no-spam) or just make a statistics to evaluate
the work of the anti-spam filter using a corresponding scripts. In this case
the usage cannot give enough reliable results because the algorithm LMTA
don't have a exact parameters for its work but have only a partial restored
parameters. Generally, this case is recommended only for the evalaution tests
of the package TPmail (estimation of possibilities of the package's
anti-spam filter or comparison tests with other packages).
The server sendmail is not used at all. In this case it is possible
to use the same module test_lmta, but it is neccessary to have the
intermediate module for the selected mail server. At present time a such
external filter is made only for the server Communigate Pro.