In the past couple of years personally I have been moving away from mailers and have been viewing email increasingly as a web-based
Because I use a bunch of different machines (currently five: Windoze + Linux, at home and office, plus a laptop) it would be a pain to keep them in sync. It is much easier to just keep the mail on its server and view it on the web.
With my personal mail address, every now and then I will download from the server onto a mailer, and delete from the server. So the mailer has really just become a backup tool. The average mailer "looks and feels" more like a database/information organizer than a communication tool, doesn't it? And I am making use of this aspect of it. I hardly ever send mail from a mailer.
Using a mailer as a backup tool may be akin to the way a cell phone is not really a telephone, but rather a kind of tranceiver device packaged as a telephone.
Perhaps if this kind of usage of email increases then web-based mail interfaces will be equipped with increasingly powerful and customizable options for download, backup and restore in the future.