[Evolution] POP3 mbox performance and auto-expunging?

[Jeff <web kiddo free fr>]

Hello,
I'm considering using Evolution for my aunt who let her Thunderbird POP3 mailbox corrupt itself again.

It's the second time that her inbox grows over 2 GiB (4.7 GiB this time). When that happens, well, the mail client will be slow as molasses and return the wrong messages (or nothing at all) when trying to open them, indicating a corrupt mailbox index at first glance. You'd think that just deleting those Thunderbird index files would fix the problem, but no, it deletes the mail.

So, I've had enough, and want to stop screwing around with that mail client that can't handle decently all the powerpoint-crap-coming-down-the-pipe, and make her use my beloved Evolution for the POP3 account. I guess it would be in mbox format, since, reading this mailing list, that there doesn't seem to be an easy/official way to use maildir(?).

I'd like to ask a few questions regarding Evolution's performance under a theoretical worst-case scenario.

Let's imagine that evolution has a 10 GiB mbox file for the inbox (worst case scenario). Has any of you experienced corruption or big performance problems with situations like that?

Secondly, as I understand from looking at http://www.go-evolution.org/FAQ#I_deleted_a_bunch_of_mail_but_my_mailbox_is_just_as_big_as_before._Why.3F

...it seems to me that 
- expunge = compressing the mbox file of a folder to make it more efficient
- emptying the trash = compressing all the mbox files.

As I know that there is an option in the preferences to empty the trash "on exit", "daily", "weekly" or "monthly", if I activate it, can I safely assume that, as long as my aunt puts big/useless mails in the trash, they will be completely purged automatically, and that the inbox folder size should not grow to unmanageable sizes, therefore acting like an "autoexpunge/cleanup" option? I want something that requires ZERO interaction here, because said user has the bad habit of replying "No" to "do you want to compress the folders" prompts and such.

To summarize my questions:
- will setting the trash to empty itself daily ensure that when the user trashes mail, it doesn't sit there for years "waiting to be compressed" like in thunderbird?
- in the event that this does not prevent a huge mailbox (>1 gb), would evolution still be able to manage multi-gigabyte mailboxes?
- has anyone experienced mbox index corruption much?

Of course, I know that I can ask for no guarantee or anything, I just wish to hear your stories of reliability so far. If that matters, the system uses Evolution 2.22.x on Ubuntu 8.04.1.

I look forward to your insights and experiences.