In the composing, replying, or forwarding message window, you can quickly subscript or superscript the selected in the message body with hotkeys.

Select the text you will subscript, and press Ctrl + = keys to get it done.

Select the text you will superscript, and press Ctrl + Shift + + keys.

When composing, replying, or forwarding an email in Outlook, you can easily subscript or superscript the selected text with the Subscript or Superscript buttons in the Ribbon.

1. In the message body, select the text you will subscript or superscript.

2. Go to the Font group on the Format Text tab, and click the Subscript button  to shrink the selected text to very small letter under the line of text, or click the Superscript button  to shrink the selected text above the line of text.

Now the selected text has been subscripted or superscripted as you format.

Alternatively, you can also open the Font dialog and format the selected text as subscript or superscript in the message body.

1. In the message body, select the text you will subscript or superscript.

2. Click the anchor  at the bottom-right corner of the Font group on the Format Text tab to open the Font dialog.

3. In the Font dialog, enable the Font tab, tick the Superscript or Subscript options as you need, and click the OK button.

So far, the selected text has been subscripted or superscripted below/above the line of text in the message body.

You can easily change the subscript or superscript text to normal with selecting the subscripted or superscripted text and clicking the Subscript button  or Superscript button  on the Format Text tab.