PHP Mobile Mail is aimed at mobile professionals
who want to use their favorite MUAs (noteably pine
or mutt) on their laptop, either in UNIX or Windows
(under GNU Gygwin). This lets you work offline. It
includes a mail_spooler program, which accepts the
output of you MUA and spools (on, or offline).
When connected, another process parses through
the spool and sends your messages. It is also
designed to "fake" using your REAL email address
with free services like gmx.net, or mail.yahoo.com,
when using their POP and SMTP servers, assuming
you have a domain and account that you can
control to this degree.