Not sure about other webmails, but on my hotmail account, I didn't log on for about 6 months in 2010 and they deleted the account because of this. The email name was "available" again, so I just re-created an account with the same name. Then in 2012 someone complained that I didn't answer their email in 2 years, yeah... that's because hotmail deleted my account and all my messages! lol. I noticed this again later with a few other hotmail accounts I created as well, if you don't log in for about 6 months... they remove it and all the emails sent to it. What is still kept in the cloud after they delete the account and make the name available again, I'm not sure, I'm guessing nothing (as they probably delete inactive accounts to save space) but you never know.