That point aside, both KMail and Evolution have features that might benefit the other. In KMail, the Send Later option gives you the chance to have second thoughts if you are in the middle of a heated discussion -- although it could be more conspicuous than it is. The ability to view all headers or to glimpse an attachment and compress, encrypt, or sign it, each with the selection of a box are also conveniences.
Similarly, KMail might benefit from Evolution's ability to display attachments in list or icon view. Heavy users of emoticons might also appreciate being able to select a large library of them from the Insert menu (even though most people probably don't remember more than two or three). Most of all, though, users might appreciate the easy selection of signatures in Evolution via a combo box at the top of the message, an arrangement far easier than switching KMail's identities. In the end, though, all these options are mostly minor, a matter of preference, or counterbalanced by equally handy small features in the other mail reader.
Both KMail and Evolution provide spell checkers, message templates, and filters for both spam and the organization of incoming messages into separate folders. So far as basic functionality goes, these features offer little to choose between them.
Yet, when ease of use is considered, Evolution frequently edges out KMail for one simple reason: KMail's display of unnecessarily geeky notation. For instance, in the templates, the date format is listed in KMail as "%ODATE". Similarly, the default name for a filter from an Internet.com address is FROM>: Internet.com. Admittedly, neither is that difficult to parse, but should inexperienced users even be allowed a glimpse of such notation?
Yet against such unnecessary glimpses behind the scenes, you also have to set the fact that elsewhere KMail has more options, including anti-spam and anti-virus wizards, and more options available higher in the hierarchies of menus and windows.
Verdict: Tie. KMail would win if it lost the geeky notation.
Eight or nine years ago, Evolution seemed a sophisticated application and KMail one that was barely beyond basic functionality. Now, they have almost reversed themselves.
Not that Evolution has devolved into basic functionality. But its development has slowed significantly in the last four years. Meanwhile, KMail has been on an opposite trajectory, adding features and functionality that, while often minor in themselves, add up to a convenient and highly customizable application. Now, in their latest releases, Evolution can sometimes equal KMail in features, but it rarely seems to exceed it.
Still, this is a decision on points, not a knockout blow. Both Evolution and KMail have features that would benefit the other. Just as importantly, KMail has some minor annoyances that it might lose, or at least provide the ability to turn off.
Many users, too, might prefer Mozilla Thunderbird, rather than either default mail reader. Yet, with a few qualifications, KMail emerges as the default mail reader that gives the most satisfying user experience, especially for those who want to customize.