Exchange 2010 Alias Names

Hi Folks,

I have a question concerning the use of Aliases in Exchange 2010.

We have a user who has two mailbox accounts, where the old one will be marked for deletion (account name and domain name changed here for obvious reasons):

Old mailbox account - john.smith2@defence.com  
New mailbox account - john.smith3@defence.com

We need to setup the old mailbox account above as an alias on the new account john.smith3@defence.com, such that any emails sent to the old address will be sent to the john.smith3@defence.com.

1. Will the alias work if the old mailbox account is disabled?
2. Will the alias work if the old mailbox account is deleted?
3. It seems the old SMTP address  john.smith2@defence.com cannot be added as an alias, since it claims the account still exists?

Thanks in advance