I'd like to put forward the following patch for dovecot-sieve.
Essentially this just merges in some changes made in CMU sieve 2.3.8 and as such brings the behaviour more in line with RFC 3834 "Recommendations for Automatic Responses to Electronic Mail":
fixes erroneous sender "-request" substring match
checks for existence of a selection of list-* headers
expands "named-as-recipient" header checks to "Resent-To", "Resent-CC" and "Resent-BCC" fields. Note that the appended patch also includes a fix for some missing parentheses in the "resent-to" test which resulted in some extra work being done but was otherwise harmless. The fix has been sent to cyrus-bugs+@andrew.cmu.edu
prefixes subject in response with "Auto: " rather than (non-expanding) "Re: "
I also, mostly for kicks, attach two sieve-like scripts that attempt to encapsulate the when-not-to-respond logic as implemented (if the patch were to be applied) and as advised by RFC 3834 respectively. I wrote these as an exercise to help me gain a better understanding of sieve and the CMU implementation. I'm not sure they are otherwise useful.