Originally I thought the problem was just with my email, which I have reported about seven times over the past few months. It seems to stem from the November 2020 Security update. Anyway, I am unable to attach anything in my email from Safari, or from other websites (Faxzero, Hartford, among others), so it is obviously a Safari error. How do I know? Because after doing all of the normal clearing cache and all, and still no benefit. I downloaded Firefox at the suggestion from one of the companies mentioned. Although I have only used Safari for years, and did not want to download another browser, I reluctantly did so, and I was able to attache files in each of the three above mentioned companies, as well as others. It is obviously a Safari issue. I am using Mojave 10.14.6 and Safari 14.0.2