| 1 | TRANSPORTS: |
| 2 | |
| 3 | A delivery attempt results in one of the following values being placed in |
| 4 | addr->transport_return: |
| 5 | |
| 6 | OK success |
| 7 | DEFER temporary failure |
| 8 | FAIL permanent failure |
| 9 | PANIC disaster - causes exim to bomb |
| 10 | |
| 11 | The field is initialized to DEFER when the address is created, in order that |
| 12 | unexpected process crashes or other problems don't cause the message to be |
| 13 | deleted. |
| 14 | |
| 15 | For non-OK values, additional information is placed in addr->errno, |
| 16 | addr->more_errno, and optionally in addr->message. These are inspected only if |
| 17 | the status is not OK, with one exception (see below). |
| 18 | |
| 19 | In addition, the addr->special_action field can be set to request a non-default |
| 20 | action. The default action after FAIL is to return to sender; the default |
| 21 | action after DEFER is nothing. The alternatives are: |
| 22 | |
| 23 | SPECIAL_NONE (default) no special action |
| 24 | SPECIAL_FREEZE freeze the message |
| 25 | SPECIAL_WARN send warning message |
| 26 | |
| 27 | The SPECIAL_WARN action is the exception referred to above. It is picked up |
| 28 | only after a *successful* delivery; it causes a warning message to be sent |
| 29 | containing the text of warn_message to warn_to. It can be used in appendfile, |
| 30 | for example, to send a warning message when the mailbox size crosses a given |
| 31 | threshold. |
| 32 | |
| 33 | If the transport is handling a batch of several addresses, it may either put an |
| 34 | individual value in each address structure, and return TRUE, or it may put a |
| 35 | common value in the first address, and return FALSE. |
| 36 | |
| 37 | Remote transports usually return TRUE and local transports usually return |
| 38 | FALSE; however, the lmtp transport may return either value, depending on what |
| 39 | happens inside it. |
| 40 | |
| 41 | **** |