You might try putting in some debug prints to a log file you could check later (the contents of the %Env hash might be particularly useful if you suspect it's a security problem.

And while you say you're not trying to be too pretty yet, it strikes me as significantly easier to use one of the several mail modules (which would make it easier to debug, as well!) instead of doing raw socket writes. You might also investigate Archive::Zip (and Compress::Zlib) to do your zipping for you, too.

There's something to be said for building the walls and the roof out of pre-cut lumber rather than trees you uproot yourself.