I think there is a middle ground here.
Bulk mail-outs are a no brainer. If the recipient didn't sign up for it then it's spam.
External to this forum, individual (and I mean properly personalised, not just fill-in the blanks) emails that may not be directly solicited, but are indirectly solicited via requests on websites and so on, are not spam.
There is considerable grey-area in the previous item that can really only be dealt with on a case-by-case basis. Intention counts for a lot.
Internal to this forum the rules are defined in the guidelines as interpreted by the moderators, with the important proviso already given by Dr Drib. "when discovered and/or reported by a member". That's an important proviso. I have received various unsolicited private contact on this forum and I treat them like I do unsolicited emails: if it's individual, courteous, non-intrusive contact, of specific relevance/interest to me, as most have been, then I don't consider the contact to be spam. But I also know that if someone steps too far over that line then I have moderators to receive a complaint - a service that would be so wonderful to have on my email and blog.
