Integration Method 1

This method does not require any modification to the exim source code. The only action required is editing some configuration files. Once configured, an email will be handled as follows :

1. exim receives the message and stores it in the queue
2. exim delivers the message to itself. Specifically, the message will be transformed by the transport_filter then passed on to the destination of the pipe. The destination of the pipe is exim itself; communicating via the BSMTP (Batched SMTP) protocol.
3. exim receives the message again (as a new message) and queues it. This time, however, the flag $received_protocol is set to spam-scanned in order to avoid a mail loop that can be created here.
4. exim delivers the (``new'') message a second time. This time the message is delivered as it normally would (to the user's inbox or through procmail or via expanding their .forward file or whatever).

As you can see in the handling above, exim handles each message twice, giving it a new queue id the second time. In addition, spamassassin scans each message separately for each recipient.