Re: [exim] Should MX offer TLS ?

Bryan Rawlins wrote:
> This has me curious, I'm going to try and compute a probability that a
> messages is/is not spam based on if the sending server uses TLS.
> Probablities will be calculated based on results of our existing filters
> and will not be influenced by the data collected.
>
> I'll post results to the list after approximately 24 hours.
>
Here's the results of around 23 hours worth of data.

Some things to keep in mind:
Over this time period we estimate 70%+ of our volume was rejected at the
firewall/SMTP conversation level and thus is NOT factored into these
numbers. (We don't track the 'low hanging fruit')

Not all mail judged by the system is then used as feedback, so these
numbers aren't a good indicator of absolute volume, but should be
statistically accurate.

Our filtering engine is proprietary, written fully in-house, so results
with other systems may vary.

Total:
122383 Spam
32594 Ham

No TLS/SSL:
122383 Spam
27057 Ham

TLS/SSL:
1064 Spam
5537 Ham

My $0.02, It appears to be a useful as an indicator to influence an
overall score (eg. spammassassin), but as with many other things it
doesn't appear to be good for making an absolute decision based on just
this information.

As an aside I also tracked what cipher was being used, albeit for a
shorter period of time.

Totals:
948 Spam
4525 Ham

sslv3:aes256-sha:256
23 Spam
39 Ham

tlsv1:aes256-sha:256
871 Spam
3781 Ham

tlsv1:des-cbc3-sha:168
33 Spam
273 Ham

tlsv1:aes128-sha:128
1 Spam
9 Ham

tlsv1:rc4-sha:128
14 Spam
160 Ham

sslv3:des-cbc3-sha:168
0 Spam
7 Ham

tlsv1:rc4-md5:128
6 Spam
244 Ham

sslv3:rc4-md5:128
0 Spam
12 Ham


Bryan Rawlins
Systems Administrator
OnlyMyEmail, Inc.