I highly doubt this is connected
Usually this is from LinkedIn, GitHub, etc scraping... There are databases where they just guess and verify emails too
Don't forget amazon.
Yeah. This information is insanely easy to get.
98% I look at a LinkedIn profile, my $SALES_LEAD Chrome extension shows me their email + phone.
(To be clear, not from LinkedIn, but given their name/city/company.)
OP literally described a timescale for (not spam) to (spam) and you described a few possible options (basically a knee jerk reaction, with no evidence).
The medical world uses the terms indications and contraindications. I think we in IT could do with a similar process/procedure.