Works with K 9 - tmatz/k-9 GitHub Wiki

Many other Android applications build on K-9's functionality. Searching for K-9 in the Android market will turn up lots of things; here are some of the more useful-looking ones. Please feel free to add longer descriptions.

Security / Encryption:

• APG - GPG Email Encryption for Android
• X509Tools

Widgets:

• Email Widget - Fancy mail preview and count widgets (paid)
• K-9 Data Killer - Allows you to manage background sync
• MailListWidget for K-9 - Mail list preview widget
• Mail Widget - Mail preview widget

Notification:

• SMS, my Car and Me - Reads out received emails
• Email Popup - Popup dialog notification on incoming message
• MetaWatch Community Edition - Displays received emails on the watch screen, along with an unread count widget

Utility:

• K-9 Mail Locale Plug-in - K-9 Mail Locale Plug-in gives you the power to control K-9 Mail polling frequency, push and poll mail folder choices, and display theme based on time-of-day, battery level, or other conditions using Locale.