The inability to send, reply, or forward emails can be caused by a program on your computer that prevents the Yahoo! Mail Rich Text toolbar from launching properly. As a workaround, try switching to plain text mode when you send an email.

To switch to plain text mode:

1. Sign in to Yahoo! Mail.
2. Click the Compose button to start a new email.
3. Click the double arrow button (<<) at the right side of the formatting toolbar (just below the email's subject line). This switches you to plain text mode.
4. Compose and send your email.

If you continue to experience issues: 

1. Verify that you are signed onto your computer as an administrator. The administrator has all the rights to make changes on the computer and can remove Internet access, disable scripts, macros or the ability to install new software. While this is the default on home computers, it's important if you're in a work or shared computer environment. If you're uncertain, please check with your computer vendor or help desk to verify your computer's settings.
2. Follow our browser troubleshooting steps. If the steps above didn't help, the most likely cause of the problem is your internet browser.