For each connection to Haraka there is one connection object.
The remote IP address
The rDNS of the remote IP
Either 'EHLO' or 'HELO' whichever the remote end used
The hostname given to HELO or EHLO
A safe object in which you can store connection-specific variables
The current transaction object, valid after MAIL FROM, and destroyed at queue time, RSET time, or if MAIL FROM was rejected. See the Transaction Object documentation file.