Every version of QuickMail has release notes saying what was added, changed and fixed in it. They are all on the web, newest first, at QuickMail Release History.
Each version has its own page there, and every page links to the versions either side of it, so you can read back as far as you like. The list starts with version 0.5.0 in May 2026.
To find out which version you are running, open Help → About QuickMail. If you installed QuickMail with the installer it updates itself, so you are normally on the newest version already.
The same notes are on each version’s own page on GitHub, alongside that version’s downloads, at github.com/kellylford/QuickMail/releases.