Some shared connection (a family member, maybe?) probably let LinkedIn scan their mailbox without fully understanding the repercussions. If that person had a p

Some shared connection (a family member, maybe?) probably let LinkedIn scan their mailbox without fully understanding the repercussions. If that person had a persistent inbox like gmail, and ever been in email contact with the both of you, it probably inferred a connection that way. Or maybe it saw an incoming email where both of you were in the recipient or CC list. It’s really creepy what they do, and it enables them to learn all kinds of information about somebody. That person doesn’t even need to have ever visited LinkedIn; it can be provided entirely by other people.