imap plan:

flags:
    system flags are described in the imap protocol as 
words like: \Answered
the backslash is annoying to type and I think that the 
text is case insensitive anyway.
we'll represent these flags by keywords (e.g :answered).


    


todo:
    uid (modifier to copy fetch and store commands)
    


search sexpressions (things that can be passwd to the search-mailbox
function).
kwda - keywords that don't take any arguments
kwdb - keywords that do take arguments


ssexp :=  nil | ssexp1
ssexp1 := kwda | (kwdb oprnd+) (and ssexp1*) | (or ssexp1*) | (not ssexp1)
          | set 
set := number-seq | ( number-seq+ )
number-seq := integer | (:seq integer integer)
kwda := :all | :answered ...
kwdb := :bcc | :before ....
oprnd := <the appropriate lisp object for the keyword>








implemented:

  connecting:
    make-imap-connection    

  after connecting:

    fetch-letter
    mailbox-list
    noop
    search-mailbox
    select-mailbox