I just found out that two e-mails, which I received weeks ago, were erroneously filtered into the spam folder. I was completely unaware of this. The messages in the spam folder are deleted after 30 days, so it is possible that some messages were sent to the spam folder and later deleted without my knowing.
I am sorry if this happened to you. If you sent me an e-mail more than 30 days ago, but never received my reply, please let me know.