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0756eb3c PH |
1 | $Cambridge: exim/src/src/transports/README,v 1.1 2004/10/07 13:10:02 ph10 Exp $ |
2 | ||
3 | TRANSPORTS: | |
4 | ||
5 | A delivery attempt results in one of the following values being placed in | |
6 | addr->transport_return: | |
7 | ||
8 | OK success | |
9 | DEFER temporary failure | |
10 | FAIL permanent failure | |
11 | PANIC disaster - causes exim to bomb | |
12 | ||
13 | The field is initialized to DEFER when the address is created, in order that | |
14 | unexpected process crashes or other problems don't cause the message to be | |
15 | deleted. | |
16 | ||
17 | For non-OK values, additional information is placed in addr->errno, | |
18 | addr->more_errno, and optionally in addr->message. These are inspected only if | |
19 | the status is not OK, with one exception (see below). | |
20 | ||
21 | In addition, the addr->special_action field can be set to request a non-default | |
22 | action. The default action after FAIL is to return to sender; the default | |
23 | action after DEFER is nothing. The alternatives are: | |
24 | ||
25 | SPECIAL_NONE (default) no special action | |
26 | SPECIAL_FREEZE freeze the message | |
27 | SPECIAL_WARN send warning message | |
28 | ||
29 | The SPECIAL_WARN action is the exception referred to above. It is picked up | |
30 | only after a *successful* delivery; it causes a warning message to be sent | |
31 | containing the text of warn_message to warn_to. It can be used in appendfile, | |
32 | for example, to send a warning message when the mailbox size crosses a given | |
33 | threshold. | |
34 | ||
35 | If the transport is handling a batch of several addresses, it may either put an | |
36 | individual value in each address structure, and return TRUE, or it may put a | |
37 | common value in the first address, and return FALSE. | |
38 | ||
39 | Remote transports usually return TRUE and local transports usually return | |
40 | FALSE; however, the lmtp transport may return either value, depending on what | |
41 | happens inside it. | |
42 | ||
43 | **** |