I have an iMac running 10.5.8 and recently a situation developed whereby either opening the native email program or opening email and then a message will hang the entire system to the point of it being unresponsive, at this point there is no other option but to hard power the system off. I have opened the email program, clicked on the mailbox and clicked 'rebuild' this had no effect. I have booted into safe mode and copied the folders to the desktop from the following paths:
I then rebooted normally and let the mail app import all the messages, the system then behaved the same way by hanging the system upon opening an email message.
There does not seem to be any consistancy to the issue, any email message opened hangs the system, if the email app is not opened the system is fine and this is only affecting one user in the office. The problem can be traced by to starting on one particular day and ever since then, before this day it was fine. This problem could be causd by an errant message or attachment, its just difficult to troubleshoot when I can't get into the mail app or I can, but once I open a message the system hangs.
To find out if it's system wide or user specific, try this...
Open System Preferences>Accounts, unlock the lock, click on the little plus icon, make a new admin account, log out & into the new account.
Does Mail work in the new account?
Or, login via a browser & use WebMail to see the last recieved or sent eMail & perhps delete it there.