An alternative transfer agent.
WHAT IT IS
A transfer agent with a single configuration file and a flexible processing model.
WHAT DISTINGUISHES IT
Extensive configurability through routers, transports and access control lists.
WHAT ROUTERS DO
Decide how a recipient address is handled.
WHAT TRANSPORTS DO
Perform the actual delivery.
WHAT ACCESS CONTROL LISTS DO
Apply policy at each stage of a connection.
WHY IT IS COMMON ON HOSTING SERVERS
It integrates well with control panels, and its flexibility suits shared hosting requirements.
WHAT THAT FLEXIBILITY COSTS
Configuration that is powerful and easy to get wrong.
WHAT TO BE CAREFUL WITH
Rules permitting more relaying than intended Filters that can be manipulated Configuration changes made by a control panel being overwritten
WHAT TO CHECK ON A SHARED SERVER
Per-account sending limits Whether outbound mail is rate limited Whether compromised accounts are detected
WHY THAT MATTERS ENORMOUSLY
One compromised account sending in volume damages the reputation of every address on the server.
WHAT TO MONITOR
Outbound volume per account, and queue growth.
