I find that GitHub is an incredibly useful way to find email addresses since git commits have email addresses included. Also, many conference talks end up on Youtube. Conference talks are often by senior employees and almost always include their email address on an early or late slide. “I really enjoyed your talk on XYZ, particularly the point about ABC. I’ve written on that before here: $LINK. Could we perhaps chat for 15-30 minutes about what you are doing recently at $COMPANY?” People tend to have a much better opinion of professionals who message “I will give you the opportunity to sell me on a job” versus “I want a job.”1.