A core part of an e-mail client is of course writing and sending emails. The ‘Compose’ screen of K-9 makes this straightforward.
On the action bar are icons for attaching files and sending the e-mail. The file attachment action links to an installed file manager if present.
In the compose screen itself, the account the email will be sent from is displayed. Tapping on this allows you to select a different identity to send from.
Below the From address, the To address is initially visible. Tapping the down arrow allows you to add Cc and Bcc addresses.
Depending on the settings the message body is shown below the subject, along with a reply if relevant.
Finally at the bottom the default signature is shown. This can be changed in Settings/Account Settings/Manage identities/Identity/Signature