All of this is possible in Perl (although it's possible in a lot of other languages too).

There are many email handling modules, the MIME::Parser module can easily extract email attachments (as I show in Re: Save Email Attachment to File), and there are a couple of modules that can do the uuencoding. Just about everything you need you'll find on CPAN Search.

Depending on the web service, I'm sure there's some module that handles that too.

Beyond that, I think you'd need to let us in on some details if you want specific help with something.

Good luck! :)