When comparing K-9 vs Missive, 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 Missive is ranked 19th.
Ranked in these QuestionsQuestion Ranking
Pro No privacy concerns
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 Complete PGP encryption
It's possible to complete encrypt email communications via PGP using K-9.
K-9 mail does not use too many system resources when using the app, which allow it to be fast and lightweight.
Works well with locally maintained IMAP server.
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 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 Live collaborative draft editor
In Missive you can live edit an email draft with your teammates, the draft composer acts exactly like a Google doc. Each team member has a different color cursor.
Pro Is a fully functional email client
It’s important because the collaborative part of Missive becomes useful when users consume all of their emails within the app. You not only want to collaborate around emails sent to your company help@address, but also around the really important emails you most likely receive at your personal company address, like that really important email you received from a potential high profile partner.
Supports multiple organizations with one user login.
Pro Team chat
Missive is also a team chat app. When using Missive you can ditch your email client, chat app and help desk.
Pro Unified inbox
Merge all email accounts in one unified inbox.
Pro Offers read receipt
Know exactly if and when the recipients read your important email.
Pro It works
Nicely written software. Always works as you'd expect, beautifully designed, a classy piece of software.
Pro Has emojis
You can create multiple tasks per conversation all assignable to a single or a group of persons.
Pro Gmail shortcuts
Supports Gmail shortcuts.
Con Noisy UI
The user interface is bland and tries to cram a lot of information on screen, making it unpleasant to use.
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 Dead app
Con No option to add words to spellcheck dictionary on Windows
Incredibly frustrating to see the name of your company constantly underlined in red, with no way to fix it.