On 2004-02-02 11:43:29 -0500, Alan DeKok wrote:
Yakov Shafranovich <research(_at_)solidmatrix(_dot_)com> wrote:
The SMTP protocol does not distinguish between attachements and
non-attachements, since it usually does not parse the body of the message.
That is, there is nothing within SMTP to allow a recipient MTA to
be informed as to:
a) size of the body
There is the SMTP SIZE extension (RFC 1870), which is in widespread use.
b) hints as to the content of the body
Right. That would be nice.
Right now, the recipient has to accept the entire message to obtain
this information.
If SMTP required the originator to publish the size and number of
messages they were trying to deliver, then that would provide
significant information to the recipient, which would allow him to
make better decisions about the messages.
e.g. I don't know who you are, and you want to send me a 1M message?
sorry, you get 10 kbps.
e.g. You said you wanted to send me a 1k message, and you've just
hit the 10k mark. I think I'll hang up now, and blacklist you.
The size extension (like all extensions) is optional. However, similar
policies could currently be implemented:
You can throttle the speed to 10 kbps on all unknown senders which don't
support the size extension (this won't hurt unknown senders which send
small messages much).
You can impose a small message size limit on unknown senders and either
hangup and blacklist them or reject the message after receiving it (and
blacklist them).
These sort of protocol additions have *zero* impact on trusted and
honest users of SMTP.
If the size extension is made mandatory for clients, many MTAs will have
to be upgraded or replaced. This is not zero impact. We already have a
voluntary mechanism for the client to disclose this information.
hp
--
_ | Peter J. Holzer | In this vale
|_|_) | Sysadmin WSR | Of toil and sin
| | | hjp(_at_)hjp(_dot_)at | Your head grows bald
__/ | http://www.hjp.at/ | But not your chin. -- Burma Shave
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