Description of problem:
If a message contains a MIME attachment which has the word "From" at the
beginning of a new line, Thunderbird treats this as a new message, resulting in
what appears to be a corrupted mailbox. A test case is attached - when this mbox
file is loaded in thunderbird, thunderbird shows two messages, one with no headers.

Version-Release number of selected component (if applicable):
thunderbird-1.5-6

How reproducible:
Everytime

Steps to Reproduce:
1. Place attached test case file in the directory that thunderbird looks for
messages
2.open the test folder
3.
  
Actual results:
Two messages

Expected results:
One message

Additional info: