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RE: Transparency

2006-05-16 21:17:43
At 12:43 -0700 on 05/16/2006, Tulsi Ram Mayala wrote about Re: Transparency:

Yes a sender sending a single dot is buggy. But a receiver not removing a dot in case of a single dot should not be called buggy. Maybe a better way to put it is it can throw an error ("Invalid data input" or something else).

Unless we can see what "went out over the wire" (ie: Was sent to the Receiving SMTP Server) we can not state where the error lies.

The RFC states that:

 1) .CR+LF is the signal that the transmission of the body is over.
2) When .CR+LF occurs in the body of a message to prevent it from being acted upon by the receiving SMTP Server, it is to be converted to ..CR+LF (by appending a second period. 3) To avoid needing to special case ..CR+LF at the receiving end, ANY line that begins with a period in the body is to be prefixed with a 2nd period when sent. 4) The receipt of .CR+LF by the receiving SMTP Server is an end-of-body signal. 5) Any OTHER line that begins with a period is to have that period removed and the rest of the line accepted.

What this means is that this is what gets sent:

   Input          Sent
   .              ..
   ..             ...
   ..two          ...two

So long as the string in the Sent column is received by a properly working SMTP Server then the original string from the input column will be recovered.

Now lets look at a broken sender that only adds a period if the 2nd character is NOT a period. This would cause the following:

   Input          Sent
   .              ..
   ..             ..     (not ...)
   ..two          ..two  (not ...two)

Now we see that the situation is as follows assuming a "correctly functioning" receiver (which seems to be what is occurring):

   Input          Sent       Received
   .              ..         .
   ..             ..         .
   .one       .one
   ..two          ..two      .two
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