i have tried disabling acceleration and started firefox in safe mode

Firefox Options > Applications. Look for Maito and redo its settings.

i still can't click on email address nothing pops up

when sending to an email addressThe launch app pops up now its say unable to connect

Unable to connect

Firefox can't establish a connection to the server at compose.mail.yahoo.com.

   The site could be temporarily unavailable or too busy. Try again in a few moments.
   If you are unable to load any pages, check your computer's network connection.
   If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web.

Looks that there is a problem with accessing https://compose.mail.yahoo.com, but http://compose.mail.yahoo.com works for and redirect to the secure Yahoo mail website.

Try to change the secure https protocol in the link of the Yahoo mailto pref (compose.mail.yahoo.com) to http.

• http://compose.mail.yahoo.com/?To=%s

You can open the about:config page via the location bar

• http://kb.mozillazine.org/about:config

gecko.handlerService.schemes.mailto.0.name : Yahoo! Mail
gecko.handlerService.schemes.mailto.0.uriTemplate : http://compose.mail.yahoo.com/?To=%s

I have tried everything: Microsoft Outlook Help, Firefox help as shown here. I am still in the same position: I can receive Outlook emails in Firefox, but I cannot send or reply. If I do not get an answer to this problem, I am off back to IE 11, where it works. Why has this only happened after the last 2 Firefox Updates? I do not want to leave Firefox, been here a long time, but I need to send and reply to emails, such a simple internet feature one would think!

Have you tried Microsoft Live Mail program? I do not know if it works on Yahoo.com, but it can't hurt to check. I'm set up with Microsoft Live Mail and have had no trouble with Firefox.