Comment 1 for bug 174207

With a recent thread on ML i came again across a problem with Thunderbird
that i had myself 1 or 2 years ago.

Thunderbird uses mailbox files to store mails and an aditionally *.msf file
for meta data of that mbox-file.
Now when you delete a mail in TB it only disappears in the mail pane but is
still physically stored on harddisc in the mbox.
To really delete a mail then s.o. has to "compact" that folder.

New users (or those not interrested in technic) wont notice that and then the
profile folder can become very large.
In the specific thread the OP had mails back from 2005 still in his profile
which had grown up to 2 gig.
2 gig is approximately where we come to filesystem limitations (max size per
file)

Now to prevent that i call for commend on change the default of:
pref("mail.prompt_purge_threshhold", false);

to
pref("mail.prompt_purge_threshhold", true);

that way a user gets a dialog when the threshold (default is 100kB iirc) is
reached and gets asked to "compact" (read as really physically delete all
previous in TB deleted mails) that folder.

I have searched bugzilla.mozilla.org for bugs like that and coulnd´t find
one. Also on launchpad is no similar bug report it seems.

So i would like to know is it feasible to solve that somehow?

Reproducible: Always

Steps to Reproduce:
1. send lots of mails
2. delete them in Thunderbird
3. check size of profile directory
Actual Results:
with default settings the profile is growing and growing, even when a user
delets his mails in Thunderbird.

Expected Results:
pref("mail.prompt_purge_threshhold", true);

delete mails physicaly after the default threshold (performance)