Building a mail application.. some advice appreciated

[David Southwell]

Hi

I am looking for some general advice and guidance for selecting software 
components to fulfill a proof of concept test.

I need a mail application with  features requiring that incoming mails, which 
should comply with a predetermined format, be initially examined for 
compliance with that format. 

Each sender (read user) has to be uniquely identified in the database system 
and a log kept of every mail received.

Sender verification requirements are high and, among other things, the output 
from attachment processing must provide an input to the verification system.
 
Mails that pass verification requirements are to be initially processed by the 
receiving server and the results of verification transferred to a mysql  
database.

Subsequently data  has to be extracted from the email, processed and the 
results stored in a mysql database. Processing includes the use of scripts to 
generate email responses and other functions.

Attachments  have to be extracted and passed for processing and  results 
stored  in a mysql db.

Mails that do not comply with the verification requirements need to be passed 
to another server for logging and processing.

The system has to be scaleable.

I realise I have not given a lot of detailed information but here is the rub I 
need to build, as quickly as possible, a proof of concept, using readily 
available software components.  

The OS is freebsd (currently 6.1) running postfix. 

What components would you choose for this exercise? Be able to build quickly 
and easily is the priority  for this stage and low server demand would not be 
some important at this time.

Thanks in advance for any input you can give

David