@trucmuche2005 I think that you have identified the source of the problem. I too can repeat the problem by using the webmailer through CPanel.
One cause of the problem is when phpmailer breaks long lines. The trailing dot character is moved to a new line on its own. You could try increasing the maximum line length for text format messages to a much higher value, say 200, to try to ensure that the dot character is not moved to a new line.
