You posted in the Firefox support fora queue. Firefox doesn't do email, it's strictly a web browser.

If you are using Firefox to access your mail, you are using "web-mail" such as Yahoo!Mail or Gmail. You need to seek support from your service provider or a forum for that service.

If your problem is with Thunderbird, see the Thunderbird support fora.

https://support.mozilla.org/en-US/kb/problems-with-email-how-to-find-help

Many site issues can be caused by corrupt cookies or cache.

• Clear the Cache and

• Remove Cookies

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

Type about:preferences<enter> in the address bar.

• Cookies; Select Privacy. Under History, select

Firefox will Use Custom Settings. Press the button on the right side called Show Cookies. Use the search bar to look for the site. Note; There may be more than one entry. Remove All of them.

• Cache; Select Advanced > Network. Across from

Cached Web Content, Press Clear Now.

If there is still a problem, Start Firefox in Safe Mode {web link} A small dialog should appear. Click Start In Safe Mode (not Refresh). While you are in safe mode;

Type about:preferences#advanced<enter> in the address bar.

Under Advanced, Select General. Look for and turn off Use Hardware Acceleration.

Then restart. Poke around safe websites. Are there any problems?