On Mon, 6 Sep 1999, Ronald F. Guilmette wrote:
> >(According to SMTP standards you should accept at least 100).
> I may be mistaken, but I believe that number is just a suggestion, and
> nor a requirement.
I looked at a few things after I wrote that and could not find a
requirement (or suggestion) of accepting 100 recipients. There is a
requirement in RFC 821
There are several objects that have required minimum maximum
sizes. That is, every implementation must be able to receive
objects of at least these sizes, but must not send objects
larger than these sizes.
The maximum total number of recipients that must be
buffered is 100 recipients.
As I read this, it means that a site must (actually its weaker than a
MUST but stronger than a SHOULD) accept 100 RCPT in a single transaction
syntactically, but I see nothing in there ruling out a policy of rejecting
mail because it has more than N recipients where N may be < 100.
> Ideally, if their limit is set to 10, then they should give 4xx SMTP response
> codes after the first 10 RCPT TOs (not 5xx responses) and then your MTA
> should be smart enough to send the message to just 10 Hotmail recipients
> at a time.
That would certainly be polite, but would only have a limited effect in
blocking spam, since any MTA/spam engine would retry later on the 4xx's
> If your MTA isn't smart enough to do that, then I believe that it qualifies
> as being "broken".
> Note however that Hotmail was giving you 5xx (permanent) failure responses,
> not 4xx (temporary) failure responses,
I noted that, but thought that that still could be the consequence of some
anti-spam mechanism. (I've come across sites that rejected mail with
empty return paths as part of their anti-spam policies.)
> >Or is this just a temporary failure, and not the consequence of a poorly
> >designed anti-spam mechanism?
> I read something just the other day on some (Internet) industry news site
> that said that Hotmail has been having some "technical difficulties" lately.
> The problem you experienced may perhaps be related to that in some way.
The 554 problem appeared to be temporary. Later messages went through
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