What can be found out by person’s IP/host address

anonymizedemailip addresstrace

I just discovered that my supposedly anonymous e-mail isn't so anonymous after all.
My IP and host name is sent with the headers. This information exposed, what can be found out?

Best Answer

All sorts of things -- what OS your machine (or router -- whatever's directly connected to that IP address) is running, what services might be running on there, anything that can be determined by talking to the services provided on that IP address (Windows file sharing is the best one, but even a mailserver or FTP server can provide all sorts of info).

More broadly, that IP address can be correlated with other connections you make (to websites, other e-mail, etc) as a weakish identifier.

What kind of a bollocks anonmailer doesn't strip incoming received headers, though?