I'm using Krusader in Fluxbox. Since I don't have Kmail installed, I'd like to mail files using Thunderbird.
The user action composes a new mail in Thunderbird with the current file as attachment and the subject 'Sending file'.

-- NEW VERSION (29 sep 2006)--
I've created a new version. You can now select multiple files and attach them to one e-mail.

-- BUGFIX (12 Oct 2006) --
There was a bug in my last version. I didn't work if you selected only one file.
I've uploaded the new version, my apologies for any inconvenience.