I have never experienced this...

but then I also don't use any spam filters and I personally go through every email. I also change my email address periodically. It is possible that your recipients are missing the emails, even though they come in. It is easy to do if you are getting a lot of spam or if you use a spam filter. I also save all of my sent emails. If anyone ever tells me that they never received an email I can re-send it and I even have the information about when it was originally sent.

There is a possibility that you should look into. If your email account has been compromised and used to send out spam or viruses there is a distinct possibility that your email address has been blocked by some recipients or their service providers. This can happen without you ever knowing about it. If this has happened you may find it easiest to get a different email address. In fact, I keep an email address that is reserved for nothing but personal emails and another that is for business emails. If I ever receive even one spam message on either I immediately change it. It can be labor-intensive, but I have never found a better way to fix a potential problem. My "regular" email address is not used for anything that is important. Fortunately, I have only had to change an email address because of spam a few times.