emails from certain sites are suddenly rejected as spam. I never even see them.
Why are certain emails from specific websites suddenly not being received and am told they are detected as spam?
This is a support forum for Mozilla Firefox. You will have to contact your e-mail provider for help. https://support.mozilla.org/en-US/kb/problems-with-email-how-to-find-help
Or are you talking about Thunderbird? https://support.mozilla.org/en-US/products/thunderbird