finding out whether a server has TLS, whether it uses a dnsbl, etc

[Nomen Nescio]

Is there a website or other service that keeps a record of attributes
of various mail servers?

Or an app, perhaps?

I find that telneting to 25 from a script is a bit of a tedious hack.

[David F. Skoll]

Nomen Nescio wrote:

> I find that telneting to 25 from a script is a bit of a
tedious hack.

But it's the only way to know that your info is up-to-date and
accurate.

Regards,

David.

[Sam]

The only way to tell if a particular mail server uses a particular DNSBL
would be to telnet to it, and see what happens.

And even then, the results won't be accurate. The server may very well be
configured to return an error message that would say something like "User
unknown", if the sending IP is on some particular DNSBL.

So, in order to make it logically possible for some third party survey of
which mail servers on the Internet use which DNSBL is for the third party to
have a separate IP that's listed on each DNSBL, and probe each server
independently, and even then the results will not be 100% reliable.

In other words: no such thing could ever be possible.