I'm looking to see if there are any webmail system's out there that have been designed to get past blocks. For example the local library might block out all webmail, I'm looking for something to get past this. Is there any webmail system out there to do this? This system would probably have to avoid using words like email, chat, etc.

A lot these blocks use keywords but administrators can also add sites to be blocked/filtered... So your webmail could eventually be filtered out, whether or not it doesn't have 'email' in it...