mail header parser?

I'm in the process of updating my anonymous server. Up till now, I've relied on a really brain-dead parsing of the mail headers. This is good enough essentially all of the time; it may even be good enough all of the time (on the theory that those addresses it rejects violate de facto standards even if they don't violate de jure ones). Nonetheless, if there is a simple *and* correct mail header parser (Internet and uucp-style), I'd appreciate a pointer to it. Ya know, I *hate* testing sometimes. Eventually I want to release this thing but I want a test suite to go with it -- and I think the damned suite will be bigger than the server!