Most people who just want a webmail solution do not want to
store mail in postgres, unless you are writing a specialized app
such as a knowledge management system which lets people
search over everyone's email to find the answer to a specific
problem. Something like this would be very valuable, it just is
beyond the scope of what most people want when they think
about a 'webmail' system.
note, it isn't impossible to use a database as the backend to a
standard webmail system...in fact, AOL stores all of its user mail
in sybase. it comes in handy when you need to find out which of
your users are using dirty words like 'breast' and 'pants.'
