From Bugzilla Helper:
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; Q312461)

Description of problem:
If mailbox, open by mail, gets shorter (e.g. because edited by another mail 
session) mail program will not detect that and it overwrites new mailbox with 
an old copy that it had in memory.

Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1. Open a mailbox folder with mail, make some small change.
2. Open it another time (with mail for example), delete a couple of emails and 
quit saving changes so that effect is a shorter mailbox.
3. Quit the mail program from step 1 saving changes.
	

Actual Results:  Result is the mailbox from 1) any changes made in the meantime 
are lost.  

Expected Results:  Mail should detect that mailbox got shorter and it should 
abort any changes.  

Additional info:

Mail also doesn't do any checking when mailbox got longer, what if again this 
was a result of action by another mail program.  Simple "fix" - check if added 
stuff begins with "From ".