Outlook is an email client, not an email service. Your email service is either your ISP or an independent email service, such as a free Gmail account from Google.
So, again,
Are you using the Outlook message editor or Word for email messages?
To check, go to Tools, Options, Mail Format (tab), and see whether one of the check boxes under Message format is marked. Those are two options there, both of which use Word as your email message editor.