In some incarnations, Doctor Who had a robotic dog named “K-9” The dog was, in effect, an android mutt. When Jesse first created K-9, his goal was to create an Android mail client as good as the UNIX mail client mutt. The name was a natural fit.
K-9’s icon is a picture of…well, of K-9.
This is a POP3 limitation: that protocol doesn’t report/support READ/UNREAD status. IMAP addresses this limitation.
If you see a list of mails inside of a folder and you want to get back to the overview screen, you have to
Google doesn’t let programs installed on SD run as services, which we need to do in order to be able to fetch your mail.
Do the following to replace default signature in K-9 with your personal signature for any email account or stop K-9 default signature for that particular account:
Open K-9, select email account in which you wish to create a signature. Key Sequence: Menu/Settings/Account Settings/Sending Mail/Composition Defaults
In this dialog, you can enter Your Name, Your Email Address, Bcc all messages to, CHECK (or uncheck) USE SIGNATURE, enter your signature using correct syntax of top line of signature with – followed by a line break, and enter your desired signature. Choose radio button to place Signature position before or after quoted text.
“Account settings” (via long click or Menu) > “Folders” (“Incoming server” in pre-3.400 versions)
K-9 Mail uses the standard Android way to inherit external app features (
Intents); you need a file manager application in order to choose any file.
Compatible file managers:
Please use the
Back key to leave all settings screens in order to trigger settings save.
K-9 lets you choose to only sync the most recent messages to your phone. This particuar feature operates on all messages, even if you’ve chosen to sync only the last 10 messages to your phone.
You’ve turned on “push” mail and marked a lot of folders for push. IMAP push requires one connection per folder.
K-9 normally doesn’t take much bandwidth. It is comparable to other Android mail applications such as GMail. However, there may be some situations where K-9 can consume up to 150k of bandwidth everytime an account is refreshed.
This normally happen when you have a POP account that has a huge inbox folder. If you have a inbox of about 2500 messages in it, it would generate data exchange between K-9 and the POP server in the order of 120k per refresh query.
For the website see: the K-9 website source code
We only publish release notes for stable releases (see next question) that are also pushed to Google Play (formerly Android Market).
4.0xx = stable / Google Play (Market)
4.1xx = unstable / development
4.2xx = the next stable
4.3xx = the next development
See the pattern? If the digit after the dot is even, it’s a stable release. If it is odd, it’s a development release.
Stable releases are changed only minimally when necessary, and should work just as well or better for all users when changed (i.e. going from 4.004 to 4.005). These are released to Google Play (formerly Android Market). It’s a good idea to always update these, as they contain serious bug fixes and security updates, but you probably won’t see anything different.
Development releases are the latest and (hopefully) greatest, but may introduce new bugs or break things that were working before. You might find that K-9 no longer works on your device with an older version of Android (somewhere in 4.1xx we quit supporting Android older than 2.1, which means that K-9 4.2xx will only support Android 2.1 and newer). This is where new features happen (as well as bug fixes and security updates), and by using development releases you can help us to spot and fix new bugs early.
Every version of K-9 is available to be downloaded here. They are sorted by date, most recent first, and you can see that some 4.0xx releases are listed above some 4.1xx releases. Often a 4.0xx release will happen at the same time as a 4.1xx release.
Depending on what type of account you have configured, K-9 may support either push or poll for fetching new mail (see Account settings > Fetching mail). At this time, K-9 only supports push for IMAP accounts.
Polling refers to the mail client periodically asking the mail server for new mail, on some configured time increment.
Pushing refers to the mail client keeping an open connection to the mail server, so that the server can inform the client of new mail as soon as it is received.
Pushing typically uses more battery than periodic polling. First, when you have any account configured to push, this keeps an Android service running at all times. This service keeps 1 open connection to the mail server for each folder configured to push (which also uses battery power). And lastly, pushing will typically lead to more frequent communications between the client and the server.
With polling however there is a delay between an email arriving and it being received (e.g. if it arrives just after the last poll it will be delayed for nearly an entire poll interval). At higher poll rates, the overhead of polling and not receiving any messages, plus the near constant connection being open makes it less battery efficient.
It will say this if there is no network, or if there are no folders set up to pull or push (inbox by default will), or if pull and push are both disabled, or if syncing is disabled for all K-9 accounts.
Most of these settings are under Settings > Account settings > Fetching mail. See Folder poll frequency, Poll folders, and Push folders. To change a folder’s class, long-press on the folder and select Folder settings.
The global K-9 setting is under Settings > Global settings > Network > Background sync.
If you are using Andriod version 6 or later, you are also likely to suffer from problems related to the “Doze” battery saving feature. For more information and potential workarounds see ticket 857 in the K-9 GitHub repository.
K-9 currently does not automatically update the list of folders. To refresh, while viewing the current folders, select Menu > Folders > Refresh Folders. This will also delete folders from K-9 that have been removed from the server.
When you start K-9 it goes to the inbox (or Unified Inbox if that is setup)
1) At the top to left of the word Inbox there is the Dog Icon and to Left of that is a small < (less than symbol once)
2) Tap once brings you to folders
3) Tap it a second time brings you to Accounts
4) Now from that screen you can tap the menu button (left of home button on G3). That will pop a menu where the first item is “Add Account”
Note: If you are using Unified inbox, you only need to tap the < (less than symbol)
1) Start K-9
2) Tap Menu > Settings > Global Settings >Interaction
K-9 has no fixed release schedule. Nor does it have any full-time developers at time of writing. Fixes to bugs and enhancements are done by interested developers according to their own priorities.
In terms of releases: