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| -rw-r--r-- | src/transports/README | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/src/transports/README b/src/transports/README new file mode 100644 index 0000000..9ea29fb --- /dev/null +++ b/src/transports/README @@ -0,0 +1,41 @@ +TRANSPORTS: + +A delivery attempt results in one of the following values being placed in +addr->transport_return: + + OK success + DEFER temporary failure + FAIL permanent failure + PANIC disaster - causes exim to bomb + +The field is initialized to DEFER when the address is created, in order that +unexpected process crashes or other problems don't cause the message to be +deleted. + +For non-OK values, additional information is placed in addr->errno, +addr->more_errno, and optionally in addr->message. These are inspected only if +the status is not OK, with one exception (see below). + +In addition, the addr->special_action field can be set to request a non-default +action. The default action after FAIL is to return to sender; the default +action after DEFER is nothing. The alternatives are: + + SPECIAL_NONE (default) no special action + SPECIAL_FREEZE freeze the message + SPECIAL_WARN send warning message + +The SPECIAL_WARN action is the exception referred to above. It is picked up +only after a *successful* delivery; it causes a warning message to be sent +containing the text of warn_message to warn_to. It can be used in appendfile, +for example, to send a warning message when the mailbox size crosses a given +threshold. + +If the transport is handling a batch of several addresses, it may either put an +individual value in each address structure, and return TRUE, or it may put a +common value in the first address, and return FALSE. + +Remote transports usually return TRUE and local transports usually return +FALSE; however, the lmtp transport may return either value, depending on what +happens inside it. + +**** |