Well I use KMail, and it is as easy as going into my home directory and doing this:
Code:
$ tar cvf mail.tar .kde/share/config/kmailrc .kde/share/apps/kmail/*
$ bzip2 mail.tar
i. e. I archive the folders .kde/share/configkmailrc and .kde/share/apps/kmail/* in my $HOME directory.
Logically, you should be able to do the same with Evolution? I. e. find its directory where it stores its configuration information and the directory where it stores your mail, then archive those...?