The first step to composing a new message is to click 
on the toolbar to open a blank compose page. You can also
right-click in the From section
of an email and select New Email,
to open a blank compose page. Depending on your Mail
preferences, the blank compose page opens in the Zimbra content pane
or opens as a separate compose window.
In the Zimbra Compose window, you enter the email address of the person or persons to whom you are sending the message in the To: field. You can look up a person's email address by clicking To in order to search through your contacts or the global address list. To add BCC addresses, click Options on the compose toolbar.
If you have more than one mail identity configured, you will need to select the identity to use before you start to compose your message.
You can either compose your message in HTML or in plain text. The default format is configured in your Options, General tab. To quickly change the format for this message only, click Options on the compose toolbar and select either HTML or Plain Text.
Format As HTML lets you format your message with different font styles, create tables, add color.
Format As Plain Text produces text with no style or formatting. Any computer can read this type of message.
Click from the toolbar. The compose
page is displayed.
If you are not using the default identity, in the From drop-down list at the top of the compose window select the identity to use.
Complete the address, subject line, and body text as needed.
If you supply a first and last name that is not in the form of a valid Internet address (name@domain.com), a confirmation dialog appears advising you that the address does not appear to be valid. You can choose to send the mail anyway, even though it may not be deliverable.
Enter the body of the message in the text box below Subject.
To check the spelling in the message, click Spell Check.
To add an attachment, click 
.
If you have a signature defined in your Options>Mail Identities but not enabled, click Add Signature on the Compose toolbar to add that signature.
Click Send to send the message.
If you don't want to send the message immediately, click Save Draft. The message is saved in the Drafts folder.