From - Fri Aug 24 11:55:47 2018
From: Author <author@example.com>
To: Recipient <recipient@example.com>
Subject: Sample message 1
Date: Fri, 24 Aug 2018 11:55:47 +0000

Later versions of Thunderbird quote things by prefixing
a space,like this:
 From 
 From - Fri Aug 24 11:55:47 2018
This could cause problems, if a reader decides to split the message
here.

From - Thu Aug 23 09:10:23 2018
From: Author <author@example.com>
To: Recipient <recipient@example.com>
Subject: Sample message 2
Date: Thu, 23 Aug 2018 09:10:23 +0000

This is the second body.