Open WebMail Project
openwebmail.org
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
Open WebMail is a webmail system based on the Neomail version 1.14 from Ernie Miller. Open WebMail is designed to manage very large mail folder files in a memory efficient way. It also provides a range of features to help users migrate smoothly from Microsoft Outlook to Open WebMail.