Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Cryoserver - Cryoserver is an all-in-one email archiving solution that empowers you to preserve your email in a tamper-evident archive, making you transform your data into a useful archive for everyday use.
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
Gmvault - Backup the emails in your Gmail account.
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.
imapsync - Console-based utility for migrating IMAP mailboxes.