edit/change mailbox

[#1]

I have at least two mailboxes set-up, which seemed useful at the time. Now however I find that I don't want to log-in seperately to check each one.
Is it possible (and if so HOW) to convert a maibox to an alias/redirect?
The obvious route /maiboxes/edit only allows a password change. Creating a new alias/redirect with the mailbox name fails. Don't know where else to look, any advise appreciated.
-Clunky solution is to forward all the old emails out, delete the mailbox, and then create a new alias on the same address. I'd rather not go down this route as it's a lot of hassle unless there is no other solution.
Thanks

[#2]

Forwarding isn't the way to go as you will then be the senders address on all the emails. If you use Thunderbird and configure both mailboxes as IMAP you can directly move the emails from one mailbox to another (it may take time if there are lot or big attachments). You could then delete the emptied mailbox and create the alias.