I am not that familiar with MS-Outlook (have used it, and set it up, occasionally, but never gone into it in depth), but I am not sure that any email reader would implement a policy where mail was stored in perpetuity.
I can imagine cases where installations would desire this for archival purposes, but this would normally be implemented by taking copies of all emails on the server, and then backing up offline when the volume became too great to leave them online. I have never seen this functionality implemented in the mail reader.
Another question I have - why do you want to do this?
The three reasons why I can imagine you might want to do this are:
1) You don't trust yourself not to delete critical emails. As I said, you do have a two stage delete, that you can configure in various ways, to partly mitigate this.
2) You are worried about someone else having access to your machine, and deleting mail items before you get to read them. Not sure how you get around them, except not give them access to your mail in the first place.
3) You want to be able to download mail on two different machines, and don't want to have the fact that you downloaded the mail on machine A to prevent you from accessing mail on machine B. If you are using IMAP as a mail protocol, then you can access mail from both machines, but by default configuration, you can delete mail from either machine. If you are using the more common POP3 protocol, then the issue is not about preventing deletion of the mail on the local machine (that is only a local copy of the mail anyway), but about not removing it from the POP3 server when it downloads the mail - this is very possible, and simply changing a setting in the Accounts that describe your POP3 set-up for each POP3 account you are downloading from.