My mother taught me to write thank you notes. Today's mothers should teach their kids to respond to emails. Trouble is, they don't respond to emails themselves.
I respond to every email I get within 72 hrs. I even respond to the Nigerian scammers: "Thanks for thinking of me, but my mother-in-law always warned against things that seemed too good to be true."
I would like to respond immediately to emails, but don't want to appear needy and pathetic. I send my correspondents interesting emails then hear nothing (with a couple of exceptions). When I see that person I ask them if they got my message. "Yeah, I meant to respond, but your email was so good, I was speechless."
A simple "Thanks" and a brief description of the local weather is all I need. So pathetic.