How do I change the text direction while composing a message?
If your Gmail interface language is set to Arabic or Hebrew, you'll be able to select either Left to Right 
or Right to Left 
directionality when composing a message. A message can contain any combination of right-to-left and left-to-right paragraphs. By default, Gmail starts composing a message with the Right to Left button active in Hebrew and Arabic interfaces.
To change the text direction:
At the beginning of a message or new paragraph:
- Click the Left to Right button
in the formatting bar of the compose window. The cursor will move to the left side of the compose pane.
Of an existing paragraph:
- Highlight the paragraph to edit
- Click the Left to Right button in the formatting bar of the Compose window
