Just thought it was a courtesy thing to let the buyer know that everything is good and item will be posted - the personal touch if you may instead of just the eBay generated message. Usually it's just a quick 2 line email followed by marking the item as posted (when it is sent). A fair few buyers even respond with a quick message to say thanks for the email and letting me know. Would be a shame if I had to stop this in the name of DSRs