Rated 5 out of 5 stars

If you are using Sieve you do no need this. You can do something like this :

require ["variables","date","fileinto","mailbox"];

# Extract date info
if currentdate :matches "year" "*" { set "year" "${1}"; }
if currentdate :matches "month" "*" { set "month" "${1}"; }

# Archive Dovecot mailing list items by year and month.
# Create folder when it does not exist.
if header :is "list-id" "dovecot.dovecot.org" {
fileinto :create "INBOX.Lists.${year}.${month}.dovecot";
And this will not loose your emails.

This review is for a previous version of the add-on (