When comparing K-9 vs Canary Mail, the Slant community recommends K-9 for most people. In the question“What are the best e-mail clients for Android? ” K-9 is ranked 2nd while Canary Mail is ranked 19th. The most important reason people chose K-9 is:
K-9 is available for free and licensed under the Apache License version 2.0 with source code available [here](https://code.google.com/p/k9mail/).
Ranked in these QuestionsQuestion Ranking
Pro Free an open source
K-9 is available for free and licensed under the Apache License version 2.0 with source code available here.
Pro No privacy concerns
K-9 mail does not use too many system resources when using the app, which allow it to be fast and lightweight.
Pro Complete PGP encryption
It's possible to complete encrypt email communications via PGP using K-9.
Works well with locally maintained IMAP server.
Pro Optimized for phone and tablet
On a tablet the UI looks a little different but given the extra real estate is logical.
Options to enable UI widgets a plus, can be enabled on a tablet and disabled on a phone.
Pro Material UI version
There is a fork of K-9 available on Google Play that uses Material design, improves the interface a lot.
Pro Excellent email threading
Threaded email support is better than most.
Pro Multiple Signatures for Multiple Accounts including ALIASES
You can assign your default signature to an ALIAS for the same account or create an altogether new one.
Pro No personal data stored on servers
No access tokens, passwords, attachments or email itself is stored on Canary servers.
Pro Seamlessly integrates with iOS verion
Gone are the days of manual setup of phone email clients! Canary Mail syncs not just your accounts but all of your settings and even signatures on iCloud.
Pro Local email database is encrypted on disk
Canary stores your local email database encrypted.
Pro Gorgeous and intuitive
Pro Pretty Good Privacy or PGP built-in
Con Dead app
Con Emails received as forwarded EML attachments are not natively supported
When you receive an email which was forwarded as an EML attachment, K-9 Mail is not able to open it natively. It opens it using a third-party application registered for this mime-type on the device, if any. The Gmail email client app is able to read the EML attachments, thus you need to have it installed as well (or any other EML capable app).
Con Noisy UI
The user interface is bland and tries to cram a lot of information on screen, making it unpleasant to use.
Con Missing mainstream features
No functionality for user-defined Gmail message-tagging, or moving/copying to IMAP folders. Might be acceptable in a free app, but not in one with premium pricing.
It adds random pins to old emails which then stay on top of the inbox list
Con Poor handling of new emails
You sometimes need to wait very long before your email actually gets delivered.
Con Windows moves randomly
When you create a new email, the new windows is often misplaced so that you have to move it to reach the "Send" button.
Con Poor text editing capabilities
The cursor is laggy so you're better off using keyboard shortcuts.
Con Show NO show
It'll show a new email on a counter, but you're not able to view them.