[achillean]

Out of ~6.5 million SMTP servers [1] on the Internet roughly 2.7 million support STARTTLS [2]. However, 1 million of them also support SSLv3 and ~200,000 still allow SSLv2.

[1] https://www.shodan.io/search?query=port%3A25

[2] https://www.shodan.io/report/PIHm43GP

[peter_tonoli]

And how many just use self-signed certificates?

[achillean]

I would assume that most of the certs w/ a chain length of 1 are self-signed so around 1.6 million (out of the 2.7 million).

[cm2187]

And 400k with expired certificates. Depressing...