Use the options on the Preferences>Composing tab as follows:
Compose: Select your default text editor, either HTML or plain text.
Set the default font settings to be used when using HTML to compose in Mail, Documents and Calendar. You can define the font style, size and color to use as your default style.
Reply/Forward using format of the original message. Even if your default text editor is different from the message received, check this box to reply to the message in the same format as received. This is useful to make sure the recipient can get the message in the best format they can read.
Always compose in new window opens a new compose window, separate from your ETCMail WebMail mailbox, when you compose a message. You can view and navigate your mailbox while the compose window is open.
Messages you compose are automatically saved as a draft every few minutes. If you would prefer not to have this automatically saved, disable the feature. You can manually save a message as a draft.
Reply/Reply All. Select whether to include the original text in the body of your reply message. You can choose to include original text, not include it, include it as an attachment, include it in the body with a prefix that you choose, or include only the most recent message. (In other words, it will quote only what was written by the person who sent the message, and not previous text.)
Forward. Select whether to include the original text in the body of when you forward a message. You can chose to include the original message and headers with the prefix below or include original message as an attachment.
Prefix. Specify whether to prefix each line with > of | for the previous email messages that are forwarded or replied to, if you chose to quote original text.
Sent Messages. By default, Save a copy to Sent folder is enabled. Copies of messages you send are saved to your Sent folder. You can check Do not save sent messages if you do not want this.