2. You can't ever know for sure but doesn't necessarily matter. The point of tor is NOT to keep your activities secret (for example, your exit node would be able to read any plaintext traffic you send, such as regular HTTP, or IRC, and also know your patterns of access - which IPs, how much data, etc) - it is to disconnect the ownership of those activities from your "real life" identity.

Assume anyone can read those emails you're sending on Tor, and act accordingly (i.e. no information that could identify you).