Leading Dots

I must be missing something here.  I noticed two MUAs, Outlook and 
Thunderbird adding extra dots for lines I would not expect it would.
For testing, I sent a simple text message with these five lines only:

.. one
... two
.... three
..... four
...... five

At my receiver, a socket read DATA block dump showed the MUAs sending 
an extra dot on each line:
... one
.... two
..... three
...... four
....... five
..                <-- expected <CRLF>.<CRLF> terminator

Why?  Is that correct?

What caught my eye was an intermediary also adding extra dots, in this 
case, a message I set to a list had a line beginning with:
     ... blah, blah

But it showed up here with two extra dots:

     ..... blah, blah

So when I begin testing why, I noticed the MUA was adding one extra 
and the intermediary adding one extra itself.
Is this normal?

--
Sincerely

Hector Santos
http://www.santronics.com