two, a default resend in Sendmail (out of the box
install) is 15
minutes - 900 seconds, meaning that the message will
be retried
AFTER 900 seconds. Generally.
If it's working the way you say, then the particular
recipient
mailhost generating that greylisting message is too
fscking
braindead to receive email.
No, Michelle is wrong. the greylist message means exactly
waht it
says, the delivery is delayed for 300 seconds. Any
retries in less
than 300 seconds are ignored. After 300 seconds, the
message is
accepted.
to end confusion i asked the greylister:))
Ken Reaburn was so kind to explain
450: ...........( Greylistet for 300 sec)
must i resend **within** the 300sec or earlyest after
the 300sec.
The basic idea of greylisting is that the sending site
should queue up
messages on a temporary error (the 450 error code),
and retry
periodically for some amount of time, where the delay
between tries and
the amount of time before the sender finally gives up
should be
"reasonable". What "reasonable" means varies, of course,
but usually a
site will retry anywhere from every 15 minutes to once
every few hours,
and will keep trying for at least 3-4 days, maybe a
week.
However, for legitimate mail, this does introduce a
delay. (There's a
lot more to it, where typically you keep track of who's
tried to send
mail from what addresses before, and if the sending
mailer does retry
the mail, then in the future, at least for a while,
you accept the mail
without delay.)
Greylisting tends to win, because most spamming software
doesn't retry
at all, and if it does, it usually retries immediately,
several times,
and then gives up. So retry attempts within the first
very short
period of time are still given the temporary failure
code; this is
probably what the "300 sec" refers to -- your mailer
should make
another attempt after 5 minutes, and the mail should
get through. But
if you're using a typical mailer configuration, you
probably are using
"reasonable" values, and the mail should eventually
go through. Resend
attempts within the 5 minute window shouldn't be a problem,
though;
they'll just get more temporary failure indications
and stay in your
mail queue.
You don't say whether the mail is actually getting through,
in the end.
But if your site and the site using greylisting are
configured
reasonably normally, it should be nothing worse than
delaying the
initial messages between parties (specifically, SMTP
envelope
addresses) at your two sites who haven't talked before
(at least,
recently).
There are some mail handling techniques that can cause
problems when a
site is using greylisting, though:
* VERP -- variable envelope return path addresses,
often but not
always in mailing lists, where the SMTP sender has a
form that may look
something like "<ListName>-<MessageNumber>-<Recipient>@hostingsite.com"
and is different for every message.
* sending server pools -- If one sending attempt comes
from one IP
address, and the next attempt comes from a different
IP address, the
typical greylisting implementation will not see them
as related, and
would treat both of them as first contacts from different
potential
spammer sites, returning temporary failures and waiting
to see if
either attempts to resend (from the same address). Usually,
there's a
timeout on how long a site can wait before resending
before the
greylist implementation throws away the data -- if you
don't retry
within some "reasonable" time, it assumes you probably
were a spammer
and gave up, so it forgets about you. Because of this,
if you've got a
large sending pool, and/or don't retry very often, the
greylist
database record for one of your sending servers might
be discarded
before that server gets around to trying to send the
message again.
In the worst case, you can try to contact the postmaster
at the site
you're having trouble with, and see if either they're
doing something
wrong, or they think you're doing something wrong, or
whatever else
might be amiss, and you can work together to fix it.
(You might also
suggest to them that in the SMTP message they send back,
since it looks
like they're trying to make it informative, they could
include a URL
for a web page explaining things a little better.)
I hope this helps....
Ken
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