hello, you're posting in the firefox support forum - firefox is a browser and doesn't handle your emails. in case you're using thunderbird as a mail client and have a question about it please say so, then we will move your question into the thunderbird queue. if you're accessing your mails through webmail, contact your email-provider in order to help you further...

Problems with email and how to find help

Are you using Firefox to access your emails, or Thunderbird?

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.

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.

Poke around safe websites. Are there any problems?

Then restart.