We actually do have a web application we use to track the challenges (the mail is all done through Mailgun).

Two things complicate managing the challenges:

* We have to actually read the code people send us (if you get things wrong, there's a pretty good chance we'll catch it). We try hard not to move people forward a level until they've gotten the previous challenges right.

* We don't dictate any particular format for submissions. Some people paste code into their email messages; some people attach lots of little files; some people attach archives. Some languages let you stick all that code in 1 file; others, like Java and C#, have complicated directory hierarchies.