When you’re sending out email to new recipients who haven’t heard from you and who may be using a variety of mail programs to view your message, it’s best to go the simplest route possible and stick with a plain text format. You won’t get any fancy formatting bells and whistles – no crazy fonts, no pictures or backgrounds – but it’s your best hope of keeping the email from landing in a spam filter or rendering as unreadable gobbledygook on the other end.
HTML, on the other hand, works great for newsletters like this one: where you’re sending to a known subscriber list and you have images, headers, and a variety of styles to manage. HTML is also a very widely recognized format, and the default for Outlook.
Rich Text is another formatting option offered by Outlook, but it’s only useful in very limited circumstances. (For example, if you're sending email within a company that uses Outlook on a Microsoft Exchange Server and want to include an attachment in the body of the message instead of up near the subject line.) Plain text and HTML are really all you’ll need to send attractive, readable emails to recipients using everything from Thunderbird to mobile phone browsers.
To alter the format of a single email, take the following steps:
Go to Actions > New Mail Message Using > And then select the format you want. (The default in Outlook is HTML.)
To change the default format for all outgoing mail:
Go to Tools > Options > And then click the Mail Format tab. A drop-down menu gives you a choice of HTML, Plain Text, or Rich Text.