Infrastructure for relaying mail through a smart host.
Traditional peer-to-peer email has been increasingly replaced by smart host configurations. Instead of sending mail directly to the recipient, a sender sends mail to a smart host. The smart host finds the mail exchange server for the recipient and sends on the message.
| Class | ManagedRelayerMixin | SMTP Relayer which notifies a manager | 
| Class | SMTPManagedRelayer | An SMTP managed relayer. | 
| Class | ESMTPManagedRelayer | An ESMTP managed relayer. | 
| Class | SMTPManagedRelayerFactory | A factory to create an SMTPManagedRelayer. | 
| Class | ESMTPManagedRelayerFactory | A factory to create an ESMTPManagedRelayer. | 
| Class | Queue | A queue for messages to be relayed. | 
| Class | SmartHostSMTPRelayingManager | A smart host which uses SMTP managed relayers to send messages from the relay queue. | 
| Class | SmartHostESMTPRelayingManager | A smart host which uses ESMTP managed relayers to send messages from the relay queue. | 
| Function | RelayStateHelper | Set up a periodic call to prompt a relaying manager to check state. | 
| Class | CanonicalNameLoop | An error indicating that when trying to look up a mail exchange host, a set of canonical name records was found which form a cycle and resolution was abandoned. | 
| Class | CanonicalNameChainTooLong | An error indicating that when trying to look up a mail exchange host, too many canonical name records which point to other canonical name records were encountered and resolution was abandoned. | 
| Class | MXCalculator | A utility for looking up mail exchange hosts and tracking whether they are working or not. | 
| Class | _AttemptManager | A manager for an attempt to relay a set of messages to a mail exchange server. | 
| Function | _checkState | Prompt a relaying manager to check state. | 
Prompt a relaying manager to check state.
| Parameters | manager | A relaying manager. (type: SmartHostSMTPRelayingManager) | 
Set up a periodic call to prompt a relaying manager to check state.
| Parameters | manager | A relaying manager. (type: SmartHostSMTPRelayingManager) | 
| delay | The number of seconds between calls. (type: float) | |
| Returns | A service which periodically reminds a relaying manager to check state. (type: TimerService) | |