On Mar 31, 2006, at 2:50 PM, Walter Dnes wrote:
One of the items I'll include in my comments about the Church draft
is his strawman approach of using statistics generated from *ONLY*
using DNSBLs. A DNSBL is merely one weapon in the arsenal of the
war against spam.
These alternatives assume dependence upon EHLO verification and rDNS
would be good enough. EHLO verification and histories based upon the
DNS would be a powerful alternative, without expecting rDNS
administration.
Assume block-lists are used and achieve 43% blocking.
Here are some maawg statistics:
http://www.maawg.org/about/FINAL_4Q2005_Metrics_Report.pdf
For an example, an institution operates a mail server and receives an
average of 50,000 valid emails/day. Assume a blocked connection on
average would otherwise attempt to deliver 3 messages with an average
size of 2KB, and that an average valid email is 6 KB. In other
words, each blocked connection represents one valid message. For
each valid email there will be on average 1.7 blocked connections and
2.2 bad emails.
With these assumptions, the numbers breakdown as follows:
50,000 ham (desired 35 msg/minute)
110,000 spam (undesired 76 msg/minute)
85,000 blocked
300 MB/day of ham
225 MB/day of spam
525 MB/day total ham/spam (49 Kb/s)
522 MB/day blocked
1047 MB/day ham/spam/blocked (97 Kb/s)
In other words, at 43% blocking the network traffic is halved.
Assume the blocking rate is 75% with a steady counter effort. (They
try harder when blocked.)
50,000 ham (35 msg/minute)
48,000 spam (33 msg/minute)
146,000 blocked
300 MB/day of ham
100 MB/day of spam
400 MB/day total ham/spam (37 Kb/s)
900 MB/day blocked
1700 MB/day ham/spam/blocked (157 Kb/s)
If the institution was a school on a DSL line, networks could be
saturated with just incoming email traffic. The overhead handling
spam and virus filtering is also sizable in terms of hardware, and
where block-lists provide real value. There is also the storage
costs when emails are archived. A reduction in the numbers of emails
stored, especially when reduced by factors of 2 or 3, adds up. Who
wants to archive spam, or have it consume allocated space in the junk
folder?
-Doug
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