You can easily change the case of the selected text in the message body with the Change Case feature as follows:

1. In the message body, select the text that you will change to uppercase, lowercase, or other style of capitalizations.

2. Go to the Font group on the Format Text tab, click the Change Case button , and then select one style of capitalizations.

• Sentence case: Capitalize only the first Word and any proper nouns in each sentence.
• lowercase: Change all letters in the selected text to lowercase;
• UPPERCASE: Change all letters in the selected text to uppercase;
• Capitalize Each Word: Capitalize every word in the selected text.
• tOGGLE cASE: Reverse the capitalizations of all letters in the selected text, change the uppercase to lowercase, and change lowercase to uppercase.

Then the case of the selected text changes as you specified.

In the message editing window in Outlook, you can also change the selected text in the message body to uppercase with the Font dialog.

1. In the message body, select the text you will change to uppercase.

2. Click the anchor  at the bottom-right corner of the Font group on the Format Text tab to open the Font dialog.
Tips: You can also press Ctrl + D keys to open the Font dialog.

3. In Font dialog, enable the Font tab, tick the Small caps or All caps options as you need, and click the OK button.

If you tick the Small caps option in the Font dialog, all letters in the selected text will be changed to uppercase, and the first letter in each sentence will be bigger then others. See screenshot:

If you tick the All caps option in the Font dialog, all letters in the selected text will be change to uppercase in the same font size. See screenshot:

1. You can press Ctrl + Z keys or click the Undo button in the quick access toolbar to clear the case formatting you set just now.

2. If you want to clear the case formatting you set long time ago, you can select the text with special capitalizations, and click Format Text > Change Case > Sentence case.