We’re going to be adding a Sieve script option for Mail Mirror to file messages in IMAP folders by date, one per day, in the format YYY-MM-DD. Some customers with mirrors that are extremely large (over 30GB inbox size) will have this modification performed retroactively since inboxes that large may have IMAP login trouble due to the index file growing too large and hitting mmap limits. For everyone else this will be a handy way to organize a mirror, especially a full domain mirror which may have thousands of messages per day.
Don’t want to wait for us? Simply add this Sieve script to your existing mirror storage mail box:
require ["date", "variables", "fileinto"];
if currentdate :matches "date" "*" { set "date" "${1}"; }
fileinto "${date}";
All we will be doing is adding the Sieve script above at mirror storage creation time (or not, if you opt out).