[Guy Harris <gharris@xxxxxxxxx>]

Srivathsan_Srinivasagopalan wrote:

>     I would like to know how SMTP (or any email application like 
> Outlook) and FTP provides information about clearly distinguishing 
> between different files which are attached and emailed at once (or 
> FTP’ed at once using mget *).

SMTP *doesn't* distinguish between them.  SMTP doesn't even *know* about 
attachments.

If you use, with a BSD-flavored FTP client, "mget *" or "mput *", the 
files *aren't* FTP'ed all at once; the FTP client transfers them one at 
a time, using separate RETR or STOR operations (along with an NLST 
operation to get a list of file names for "mget").

> I think SMTP really doesn't care about the files being attached. It 
> takes all of them in binary format and sees them as a payload. But, 
> there must be a way to clearly distinguish the end of each files being 
> attached. I think such facility is provided by the individual 
> email-clients.

Correct.  See RFC 2045 and RFC 2046 - in particular, the parts that talk 
about "multipart".  The mail message body is a single MIME entity, with 
non-text portions of the body encoded as text in some form (such as 
base-64), and with text headers separating the parts.  That body is 
transferred as a single chunk of data over SMTP.

> Please let me know the answer for the same if I use FTP.

No.  As indicated, each file is transferred in a separate FTP operation.