Zitat von Daniel Vollbrecht <[email protected]>:
Am 16.12.14 um 21:28 schrieb [email protected]:
People who are able take care of the real mail address are normaly aware
that the mailaddress is as easy to spoof as the real name. Without
digital signatures you can not really trust a mailaddress at all. You
have to verify by content then or by sideband eg. call the sender by phone.
Fully agree, but it is no plausible argument when it comes to a
reason for just hiding it away. Especially as every mail client is
able to show the From: email address which I consider as industry
standard.
Nearly all Spams arriving by the big spam farms with throw-away domains
are perfectly DKIM signed, so no, it is not a problem of "hacked"
How do you know what kind of spam I get? ;-)
accounts. If you still got spam *without* DKIM signature you should use
greylisting to keep away the dump spam-bots as they are the only ones
We deploy everything: grey-, black-, whitelisting, content filter
etc. Fortunately, the ham/spam ratio is multiple dimensions of the
ratio just a few years ago – same deployed mechanisms. Back then,
there were 10k's of spam for one ham message, now it's just a few
spams.
I still see around 40 % of non-DKIMed spam on the servers. If you
have a solution to eliminate that, I would be glad to know.
And your explanation lacks a major point: If spammers can deploy a
nontrivial mechanism like DKIM, then they easily can circumvent
greylisting - just send it again after 300 seconds. The latter costs
much less than having a proper DKIM setup, especially since they use
bot nets and cheap virtual nodes at a large scale.
That's the whole point. The spam-farms are in fact real MTA which are
able to retry *and* to do DKIM signing. Spam-bots don't do both and
fail greylisting anyway. That's why the spam reaching the inbox is
perfectly DKIM signed and therefore i will not teach our users to rely
on it.
not using DKIM. And no, content based filtering is not a option for
people who actually care about email.
Do you just use greylisting and no further server side filtering?
All just by mailbox individual learning algorithms?
I claim to actually care about email *and* use content filtering. I
only had one false positive in many years which would have been a
very grave issue if not read. Fortunately, it is easy to regularly
have a look into the spam folder. Nothing gets deleted. Saves a lot
of time and once a week (or month at the moment is sufficient) a
quick look into 'spam' does the job.
It is fine that you do but most average mail users never have a look
in a spam folder. We have seen to many e-mails ditched in some spam
folder and ceased to work with supplier which can not be reliable
reached by mail. Mail should be transactional as it is desigend. No
error means the recipient has the mail in the inbox, not in some spam
folder.
And if you care about email, you should know that greylisting might
also be fault-prone. Just have a look at the whitelist that comes
with postgrey, there are lines like 'no retry, reported by' en
masse. Even some reported fairly recent in 2011.
If the sender doesn't get a least a error message the sending server
is FUBAR and no one can expect it to deliver mail.
But that's all way OT and my last comment on this.
Regards
Andreas
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