Ok, first of all, I always remember emails that have not been answered.
I remember them like a scorned elephant remembers a decade old off-handed comment from his ex-wife.
I, on the other hand, have NEVER not returned an email.
At least that I remember.
You remember emails you sent that were not answered better than emails that you did not answer.
-Nassim Taleb, The Bed Of Procrustes