You can set the default composer mode under Settings -> Appearance -> Composer mode.
You can also switch the composer mode while typing by clicking on the “More” button and selecting Normal or Plain Text mode. The same button can be used to switch from Left to Right or Right to Left typing mode.
Normal mode (HTML)
There are multiple formatting options you can use while typing in Normal compose mode.
You can make changes to your text by using the “Bold”, “Italic”, and “Underline” buttons.
If you paste text into the composer and you wish to remove the formatting, use the “clear all formatting” button.
Plain Text mode
Plain Text mode represents only characters of readable material but excludes any graphical information and other objects (images, etc.). Plain Text is regular text, with no formatting options such as bold, italics, underlines, or special layout options.
Deciding between plain text and HTML for sending messages is widely debated, for good reason. Every email client can render plain text emails, so using this format means you never have to worry about your formatting being a stumbling block to deliverability. Plain text messages generally achieve a slightly higher deliverability rate, since they’re smaller and require less bandwidth to deliver than HTML emails. While the common perception is that all recipients prefer HTML emails because they add more visual interest, many people favor the simplicity of a plain text email.
Right to Left mode
You can use this mode only when a right-to-left language is installed and enabled in your operating system. The Right to Left mode cannot be enabled while you are using a Plain Text mode.
Click on the “More” button and select the “Right to Left” option.
You can also set the default composer direction under Settings -> Appearance -> Composer text direction.