Although such occasions are very rare, I have recently had a long server downtime which caused some loss of e-mail.
In order to prevent this from happening in the future, I am interested in having some backup, but I am not acquainted with providers of such services. The only one I have read about is the backup service provided by Zoneedit.com
Since the chances I'd ever need it again anytime soon are small, and since my e-mail traffic is reltively small - just several personal accounts - it should cost as little as possible.
Any solution you know of except the backup offered by Zoneedit.com ?
While not the answer you are looking for, if you have the resources, you might pursue setting up a MX server that routes the mail to your box. This way if your box experiences an outtage, your MX box will collect the mail until your box is back online.
Your ISP or DC should be capable of providing such a service.