On Tue, Feb 10, 2009 at 07:15:06AM +0100, Juergen P. Meier wrote:
> If everyone would use SAV, the ammount of SMTP traffic in the Internet
> would *double*. I bet most heavy duty mailssystems don't scale double.
An address probe is MUCH cheaper to process than a message. Address
probe results are cached. This estimate is likely substantially in error.
The main issue with SAV is that it can be abused to launch indirect
dictionary attacks, the target system sees connections from legitimate
MTAs doing SAV that are in turn address harvesting oracles for botnet
nodes forging sender addresses.
Another issue is that small domains that are victims of joe-job attacks
can temporarily see very high traffic loads if SAV is used by a high
volume provider (e.g. Verizon in the past).
Finally, some legitimate mail will be lost, as many developers tasked
with automating business-to-consumer email communications don't really
understand email, and just think of it as a "which API do I call to
send" problem. Questions of valid sender addresses, bounce processing,
... are foreign to them, and they are often tasking with sending messages
that could be important or time-sensitive for the recipients. SAV raises
the bar on poorly conceived/executed non-spam to a level where not all
important non-spam will continue to arrive.
These are good reasons to not use SAV or use it with caution:
- Your site should be small to very small, so that the probe
volume you emit is negligible.
- You should carefully choose which domains to SAV or exclude
from SAV.
--
Viktor.
Disclaimer: off-list followups get on-list replies or get ignored.
Please do not ignore the "Reply-To" header.
To unsubscribe from the postfix-users list, visit
http://www.postfix.org/lists.html or click the link below:
<mailto:majord...@postfix.org?body=unsubscribe%20postfix-users>
If my response solves your problem, the best way to thank me is to not
send an "it worked, thanks" follow-up. If you must respond, please put
"It worked, thanks" in the "Subject" so I can delete these quickly.
