Hi, "not optimized" can mean a wide range of things. What problems do you notice when you try to read or reply to emails in Firefox compared with Safari or Chrome? Also, does it make any difference if you sign in directly on Yahoo's site instead of on Frontier's site: https://frontier.yahoo.com/ ---- Also, thank you for sharing your addons list. I don't see any of the common blockers, but these two are curious: * Search Defender Plus (searchdefenderplus''.''com) -- currently enabled * Yahoo Search From PDF to DOC -- currently enabled * Instant Inbox (yourmailtab''.''com) -- currently disabled Judging from search results, the first and third ones are usually viewed as unwanted redirectors that interfere with searching. The second one doesn't come up in any searches. I don't know what value these are providing you, but to test with a cleaner setup, could you disable all of them? Here's how: Open the Add-ons page. Either: * Command+Shift+a (Windows: Ctrl+Shift+a) * "3-bar" menu button (or Tools menu) > Add-ons * type or paste '''about:addons''' in the address bar and press Enter/Return In the left column of the Add-ons page, click Extensions. On the right side, find the "Manage Your Extensions" heading. ''If there is at least one extension before the next heading -- "Recommended Extensions" -- please continue:'' Then cast a critical eye over the list below that heading. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything suspicious or that you just do not remember installing or why? If in doubt, disable (or remove). For your privacy and security, don't let mystery programs linger here. Any improvement? ''Note: If the Add-ons page is blank or inaccessible, please restart Firefox in its Safe Mode to finish the job:'' You can restart Firefox in Safe Mode using either: * "3-bar" menu button > "?" Help button > Restart with Add-ons Disabled * (menu bar) Help menu > Restart with Add-ons Disabled and OK the restart. A small dialog should appear. Click "Start in Safe Mode" (''not'' Refresh). Hopefully that will allow you to disable those three extensions and get a cleaner test.