You can check a site's vulnerability though at Netcraft's What's That Site Running? It will tell you if a site is running Microsoft-IIS or something different.
Spamgourmet is possibly the place you're thinking of, although I've never used them. From their website:
After you have confirmed your forwarding address, you can give out self-destructing disposable email addresses whenever you want. The disposable addresses are like:
someword.x.user@spamgourmet.com
where someword is a word you have never used before, x is the number of email messages you want to receive at this address (up to 20), and user is your username.
For example, if your user name is "spamcowboy", and BigCorp wants you to give them your email address . . . give them this one:
frombigcorp.3.spamcowboy@spamgourmet.com
This disposable email address will be created here the first time BigCorp uses it (you don't have to do anything to create it), and you'll receive at most 3 messages, forwarded to your forwarding address. The rest will be indelicately consumed.
I don't know if you can track by address what e-mail comes from what source though.
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You can check a site's vulnerability though at Netcraft's What's That Site Running? It will tell you if a site is running Microsoft-IIS or something different.