You can install from Google's Play Store:

* https://play.google.com/store/apps/details?id=com.fsck.k9&hl=en&gl=US

Or from F-Droid:

* https://f-droid.org/packages/com.fsck.k9/

Launch K9

Tap “NEXT”, K9 will ask you to enter your full c1.fi email address and password. Enter these and tap “MANUAL SETUP”

Select “IMAP” as “Account type”, And enter “Incoming server settings” as shown below:

Now tap “NEXT”. K9 is will check your settings - If the check failed please make sure you entered all information correctly. Once the test is passed you can fill in “Outgoing server settings”:

Tap Next. K9 will now test outgoing settings. If went well you will be presented “Account options”, defaults will usually work here:

Tap Next and give some name for your account (shown in K9 account listing) and your name (Shown in outgoing messages):

Tap “Done” and K9 will show your INBOX: