Internally an email server uses directories like Windows or Linux. There is nothing really unique about directories. Externally though it works in a different manner.
The "http" protocol is an internet standard that is set aside for a specific purpose that does not include email. You could probably modify an email server to allow posting the messages in an email mailbox to an apache web server directory to be able to use the "http" protocol.
http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol
Email has its own set of standards about how it works so that one email server can talk to other email servers and the DNS system. The http protocol is not part of this. So it seems like the email would need to be sent via standard email protocols and then moved to an Apache webserver directory as a copy.
http://en.wikipedia.org/wiki/Email_address
Email is pretty simple, if I were doing it I would set up an email server and an apache server on Centos5x and play with it. You can probably make it happen.
Postfix/Dovecot is a popular email combo.