On Thu, Nov 09, 2023 at 11:40:17AM -0500, Greg Wooledge wrote: > On Thu, Nov 09, 2023 at 01:47:01PM +0000, Byung-Hee HWANG wrote: > > On Thu, Nov 09, 2023 at 02:04:39AM -0500, hlyg wrote: > > > list doesn't seem to accept my mail, because of big attachment i believe > > > > > > what is max size of attachment allowed in list? Thanks! > > > This is my guess: > > > > <quote> > > 220 bendel.debian.org ESMTP Postfix > > ehlo penguin > > 250-bendel.debian.org > > 250-PIPELINING > > 250-SIZE 30720000 > > 250-STARTTLS > > 250-ENHANCEDSTATUSCODES > > 250-8BITMIME > > 250 CHUNKING > > quit > > 221 2.0.0 Bye > > </quote> > > > > So 30720000 bytes? > > That looks like an upper limit on the total message size, not the size > of a MIME attachment inside the message.
In another message, hlyg said the attachment is 1.2M, so with encoding
and things that's not very unplausible.
My take as far as now is that the message was rejected while the
protocol was "in flight" as above, and outlook.com didn't care to
generate an error message. Or you have to opt-in to an extra service
with them to be able to see them. Or something more preposterous
(Microsoft always tops my dirtiest fantasies).
> Restrictions on the message content (such as attachment size limits)
> would have to be enforced by something that parses the message body.
> SMTP receivers usually don't do that (although they may hand the message
> off to an anti-virus scanner or something which does).
This is standard nowadays. In the bad old days you did that after the
fact and had to generate a bounce message. Since the sender has control
over the address to bounce to, spammers have misused that to use MTAs
as bouncers for their stuff (mail backscatter [1]). So parsing the
message during reception ("connection-stage rejection", see also [1])
has become standard since the early 2000s, latest 2010 AFAIR.
> The OP claimed they never received a bounce, so presumably their message
> was simply dropped into the bit bucket when it failed whatever criteria
> were applied. This is sensible behavior in any kind of post-SMTP
> processing, although it's super frustrating for a legitimate sender who
> now has no idea why their mail disappeared.
Actually, no. This is behaving in non-standard ways, and, as you see
above, it is avoidable.
> So, only the list admins would know the answer.
But whose list admins. My suspicion lies with the Outlook ones
(either they don't signal the rejection, or they eat the bounce,
or they had an Azure dropout or whatever). They are known to
behave erratically already.
Cheers
[1] https://en.wikipedia.org/wiki/Backscatter_(email)
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