I'm sharing this with the list since so many members also use Academia.edu.  

A while back I had an email exchange with a list member and the same day I received an email from Academia.edu highlighting a paper by the list member I'd just been emailing.  Today I received an email from a colleague not a member of Academia.edu. That email discussed a particular hymn and had the hymns name in the email title.  Within 15 minutes of receiving that email,  I received an email from Academia.edu highlighting an article about the hymn I'd just been emailed about.

I use Gmail.  I think this means that if you are a Academia.edu member and also a gmail user, then  Academia.edu knows who and when you email someone or someone emails you, the title of the email and possibly the contents of the email.

As far as I can see looking at the Gmail privacy, Gmail doesn't say they don't share email contents and I think  to join Academia.edu you have to give them access to your contents list.

I've removed Academia.edu from access to my contacts list and hopefully this will solve the problem.

Thanks,