Well, there's still Hotmail, Yahoo, ... There is even mail.ir offering free accounts although I suppose they obey Iranian laws.
Censoring the internet is an impossible task. Everyday there's new websites rising, so to control the content and blacklist the "bad" ones (open to interpretation within the country) would be a full-time job and still an impossible task because the number of new websites and ways to bypass such filters is just growing so fast you can't catch up and censor them properly.
Also, even if a country managed to censor all "bad" sites, people can still exchange the "forbidden files" via email, Kazaa, etc... Internet censorship is pointless unless you do it the North Korean way where every site is automatically blacklisted except a very few whitelisted ones (in fact, there is only a huge nationwide intranet rather than access to the regular internet) and I would not encourage such policies.