I have been using the latest copy of version 7 of Hermes Mail to deal with certificate issues in Eudora. It helped things, but I still got certificate errors. When the latest version of the Firefox extensions fiasco started, I found a solution to deal with my legacy copy of Firefox on Reddit. The Firefox solution not only fixed Firefox, it fixed for reasons unknown all the certificate issues in Eudora. Here is the Reddit solution: "I cooked this up from the "normandy" hotfix - Firefox 56.0.2 doesn't have normandy. -----BEGIN CERTIFICATE----- MIIHLTCCBRWgAwIBAgIDEAAIMA0GCSqGSIb3DQEBDAUAMH0xCzAJBgNVBAYTAlVT MRwwGgYDVQQKExNNb3ppbGxhIENvcnBvcmF0aW9uMS8wLQYDVQQLEyZNb3ppbGxh IEFNTyBQcm9kdWN0aW9uIFNpZ25pbmcgU2VydmljZTEfMB0GA1UEAxMWcm9vdC1j YS1wcm9kdWN0aW9uLWFtbzAeFw0xNTA0MDQwMDAwMDBaFw0yNTA0MDQwMDAwMDBa MIGnMQswCQYDVQQGEwJVUzEcMBoGA1UEChMTTW96aWxsYSBDb3Jwb3JhdGlvbjEv MC0GA1UECxMmTW96aWxsYSBBTU8gUHJvZHVjdGlvbiBTaWduaW5nIFNlcnZpY2Ux JjAkBgNVBAMTHXNpZ25pbmdjYTEuYWRkb25zLm1vemlsbGEub3JnMSEwHwYJKoZI hvcNAQkBFhJmb3hzZWNAbW96aWxsYS5jb20wggIiMA0GCSqGSIb3DQEBAQUAA4IC DwAwggIKAoICAQC/qluiiI+wO6qGA4vH7cHvWvXpdju9JnvbwnrbYmxhtUpfS68L bdjGGtv7RP6F1XhHT4MU3v4GuMulH0E4Wfalm8evsb3tBJRMJPICJX5UCLi6VJ6J 2vipXSWBf8xbcOB+PY5Kk6L+EZiWaepiM23CdaZjNOJCAB6wFHlGe+zUk87whpLa 7GrtrHjTb8u9TSS+mwjhvgfP8ILZrWhzb5H/ybgmD7jYaJGIDY/WDmq1gVe03fSh xD09Ml1P7H38o5kbFLnbbqpqC6n8SfUI31MiJAXAN2e6rAOM8EmocAY0EC5KUooX KRsYvHzhwwHkwIbbe6QpTUlIqvw1MPlQPs7Zu/MBnVmyGTSqJxtYoklr0MaEXnJN Y3g3FDf1R0Opp2/BEY9Vh3Fc9Pq6qWIhGoMyWdueoSYa+GURqDbsuYnk7ZkysxK+ yRoFJu4x3TUBmMKM14jQKLgxvuIzWVn6qg6cw7ye/DYNufc+DSPSTSakSsWJ9IPx iAU7xJ+GCMzaZ10Y3VGOybGLuPxDlSd6KALAoMcl9ghB2mvfB0N3wv6uWnbKuxih q/qDps+FjliNvr7C66mIVH+9rkyHIy6GgIUlwr7E88Qqw+SQeNeph6NIY85PL4p0 Y8KivKP4J928tpp18wLuHNbIG+YaUk5WUDZ6/2621pi19UZQ8iiHxN/XKQIDAQAB o4IBiTCCAYUwDAYDVR0TBAUwAwEB/zAOBgNVHQ8BAf8EBAMCAQYwFgYDVR0lAQH/ BAwwCgYIKwYBBQUHAwMwHQYDVR0OBBYEFBY++xz/DCuT+JsV1y2jwuZ4YdztMIGo BgNVHSMEgaAwgZ2AFLO86lh0q+FueCqyq5wjHqhjLJe3oYGBpH8wfTELMAkGA1UE BhMCVVMxHDAaBgNVBAoTE01vemlsbGEgQ29ycG9yYXRpb24xLzAtBgNVBAsTJk1v emlsbGEgQU1PIFByb2R1Y3Rpb24gU2lnbmluZyBTZXJ2aWNlMR8wHQYDVQQDExZy b290LWNhLXByb2R1Y3Rpb24tYW1vggEBMDMGCWCGSAGG+EIBBAQmFiRodHRwOi8v YWRkb25zLm1vemlsbGEub3JnL2NhL2NybC5wZW0wTgYDVR0eBEcwRaFDMCCCHi5j b250ZW50LXNpZ25hdHVyZS5tb3ppbGxhLm9yZzAfgh1jb250ZW50LXNpZ25hdHVy ZS5tb3ppbGxhLm9yZzANBgkqhkiG9w0BAQwFAAOCAgEAX1PNli/zErw3tK3S9Bv8 03RV4tHkrMa5xztxzlWja0VAUJKEQx7f1yM8vmcQJ9g5RE8WFc43IePwzbAoum5F 4BTM7tqM//+e476F1YUgB7SnkDTVpBOnV5vRLz1Si4iJ/U0HUvMUvNJEweXvKg/D NbXuCreSvTEAawmRIxqNYoaigQD8x4hCzGcVtIi5Xk2aMCJW2K/6JqkN50pnLBNk Px6FeiYMJCP8z0FIz3fv53FHgu3oeDhi2u3VdONjK3aaFWTlKNiGeDU0/lr0suWf QLsNyphTMbYKyTqQYHxXYJno9PuNi7e1903PvM47fKB5bFmSLyzB1hB1YIVLj0/Y qD4nz3lADDB91gMBB7vR2h5bRjFqLOxuOutNNcNRnv7UPqtVCtLF2jVb4/AmdJU7 8jpfDs+BgY/t2bnGBVFBuwqS2Kult/2kth4YMrL5DrURIM8oXWVQRBKxzr843yDm Ho8+2rqxLnZcmWoe8yQ41srZ4IB+V3w2TIAd4gxZAB0Xa6KfnR4D8RgE5sgmgQoK 7Y/hdvd9Ahu0WEZI8Eg+mDeCeojWcyjF+dt6c2oERiTmFTIFUoojEjJwLyIqHKt+ eApEYpF7imaWcumFN1jR+iUjE4ZSUoVxGtZ/Jdnkf8VVQMhiBA+i7r5PsfrHq+lq TTGOg+GzYx7OmoeJAT0zo4c= -----END CERTIFICATE----- Save the block including the BEGIN & END lines in a text file with the extension .pem I saved mine as icfix.pem Then import the certifcate into firefox into firefox via: "Options", "Privacy & Security", down to "Certifcates" View Certifcates Select "Authorities" Import Select the PEM file Tick the checkboxes, then OK Then in the browser console Ctrl+Shift+J you run the following two lines: Components.utils.import("resource://gre/modules/addons/XPIProvider.jsm"); XPIProvider.verifySignatures(); You may need to enable the browser console input mode via about:config Set devtools.chrome.enabled to true All being well in the addons page everything should pop back to being enabled. You may need to disable & enable some of the addons to kick them into life. I had to restart to get classic theme restorer working again.