How AMG works

The path of a message

1. Your mail server sends

   The sending server connects to AMG and hands the message over as it would to any mail server.

2. AMG makes it durable

   Only after the message is written to persistent storage does AMG answer success, so an acknowledged message is never lost.

3. It is delivered across

   When the path is open, the same message reaches the mail server on the other side. If not, the queue retries.

Direction is the IP address, and nothing more

Direction comes only from the address of the server that connected. Recipient, sender, domain, headers and body never choose it, so a message with forged headers or an odd recipient cannot change where it goes. Only two addresses are allowed: exactly one mail server on each network, at fixed and different addresses, both connecting directly. A message with several recipients stays whole and goes to the server on the other side; it is not split by domain.

The message waits; it is not lost

The two networks are never connected at once, so a message waits in the queue until the destination side's turn. That wait is an ordinary deferral, not an error. A deferral carries a stable reason and the time of the next attempt. A permanent failure, or a message that outlives the queue's lifetime, ends with a standard delivery notice to the sending server; nothing is deleted silently.

When storage runs short

The undelivered queue is never deleted to make room. Retained delivered payloads go first, oldest first; if space is still short, AMG answers new mail with a temporary refusal and the sending server keeps the message and tries again later. The appliance is never the place where a message is lost.