So I have all of my old sent emails saved to the local Sent directory in Kmail, but I now want to use Evolution as my default e-mail program. Unfortunately, because Kmail does not have an Export feature, it’s not obvious how to do this. Here’s how to import e-mails from Kmail to Evolution.
1) In Kmail create a new folder: right-click on Local Folders: Inbox and select “New Subfolder”
2) Enter a name for the folder (for instance, Export) and then for “Mailbox Format” select: mbox
3) Right-click on the directory whose contents you want to export (in my case Local: Sent Mail) and select Copy Folder To and then navigate to the folder you just created (Local Folders: Inbox: Export). Wait for the contents to be copied to your new mbox folder.
4) Open a file manager (Nautilus), and select show hidden files (View: Show Hidden Files)
5) Then navigate to the kmail directory containing your new mbox folder: ~/.kde/share/apps/kmail/mail/.inbox.directory
(Note that your new mbox folder is a hidden directory within the hidden directory .inbox.directory that itself is a hidden directory inside of .kde! You won’t be able to find it if you don’t have Show Hidden Files enabled.)
6) Navigate into your mbox directory and then move the mailbox file (for instance, sent-mail) to your Desktop
7) Open Evolution and select: File: Import
8) Forward: Import a single file and navigate to the mbox file on your Desktop.
9) In Destination Folder specify what folder in Evolution you would like your Kmail e-mails to be saved in (for instance, Sent).
Your Kmail e-mails should now show up in Evolution. Repeat for each Kmail folder you want to export.