Phill Edwards wrote:
So it's a complete black box mystery as to why it just won't send a reply.
You did not specify what version of Dovecot and Sieve you are using, but, considering the lack of log messages, I am assuming it is CMUSieve. Please do indicate your setup.
According to the sources, the CMUSieve plugin will refuse to autorespond in the following situations:
The message contains a "List-Id" [RFC2919], "List-Help", "List-Subscribe", "List-Unsubscribe", "List-Post", "List-Owner" or "List-Archive" [RFC2369] header field.
The message has an "Auto-submitted" header field with a value other than "no".
The message has a "Precedence" header field with one of the following values: list, bulk, junk
There is no address to respond to, i.e. empty envelope from: no -f parameter for deliver and no Return-Path header (placed by MTA) in the message.
The sender address is the address of the user this script is running for (sender == recipient) or it is one of the addresses specified in the :addresses parameter.
The sender address is a system address, starting with 'MAILER-DAEMON', 'LISTSERV', 'majordomo', or 'owner-', or containing '-request@'.
The message is not explicitly addressed to the user nor to one of the addresses specified in the :addresses parameter. No automatic responses will be generated for implicitly delivered messages: the recipient or one of the provided addresses must be found in the to, cc, bcc, resent-to, resent-cc or resent-bcc headers of the message.
Unfortunately, CMUSieve does not indicate which condition is triggered and the vacation action is silently discarded.
Regards,
Stephan.