Just came across this and it saved not only all of my email, but also my day! Awesome stuff!

"Currently supports Gmail, Google Calendar, Microsoft Teams, Discord, Slack, CardDAV, Granola, Circleback, Notion AI Meeting Notes, Beeper Desktop, and IMAP sync, plus offline imports from Slackdump, MBOX exports, Apple Mail (.emlx) directories, PST archives, and common chat/text export formats."