Message termination dot
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RFC821 4.5.2.
  Without some provision for data transparency the character
  sequence "<CRLF>.<CRLF>" ends the mail text and cannot be 
  sent by the user.  In general, users are not aware of such
  "forbidden" sequences.  To allow all user composed text to 
  be transmitted transparently the following procedures are 
  used.

    1. Before sending a line of mail text the sender-SMTP 
       checks the first character of the line.  If it is a 
       period, one additional period is inserted at the 
       beginning of the line.

    2. When a line of mail text is received by the 
       receiver-SMTP it checks the line.  If the line is 
       composed of a single period it is the end of mail.  
       If the first character is a period and there are 
       other characters on the line, the first character 
       is deleted.


SendText() in sendmail.c makes no effort to catch message lines that begin with a period.  As a result, any period 
at the beginning of the line in a message will probably 
get removed by the SMTP server, altering the message body.
Also, a message containing a single period on a line by
itself will be terminated unexpectedly.