Interesting. I assume you have a single email address, so you can't tell the source? (I have a catch-all at my domain ⇒ I use a different email for each site, which is how I know which addresses generate spam). Is your address posted publicly in plain-text somewhere?
Yes, it is a Gmail address, from the beginning of Gmail itself. I beleive it was exposed countless times since. This thread made me think about changing that and get a new address on a personal domain.
