There seems to be two sources missing from you list of "platforms", based on some recent experiences (I'm a mail server admin and I put a lot of effort into tra

There seems to be two sources missing from you list of "platforms", based on some recent experiences (I'm a mail server admin and I put a lot of effort into tracking down and blocking spam): 1. Hotel registration. I was asked for my email address when staying at a Hyatt for the BSides Conference in SF a while back. I didn't even think twice about providing my standard email address, and within a week, started receiving a lot of extra spam. I tracked some of it down to a company that has affiliations with hotel networks, so I'm pretty sure it came from the registration process. 2. Public wifi hotspots. On this one, I dunno when or where I absent-mindedly entered my email address, but again, followed some of the spam back to a marketing company affiliated with public hotspots. Bastards. It's fairly persistent spam, and it's walking right past greylisting, SpamAssassin, and my usual filters for bad actors.