When composing, replying, or forwarding an email in Outlook, you can add strikethrough across the selected text in the message body with the Strikethrough feature easily.

1. In the message body, select the text you will add strikethrough across.

2. Click the Strikethrough button  in the Font group on the Format Text tab.

Now the strikethrough is added across the selected text in the message body.

You can also add strikethrough or double strikethrough across the selected text in the message body with the Font dialog.

1. In the message body, select the text you will add the strikethrough across.

2. Go to the Font group on the Format Text tab, and click the anchor  at the bottom-right corner to open the Font dialog.

Tips: you can also open the Font dialog with pressing Ctrl + D keys together.

3. In the Font dialog, enable the Font tab, tick the Strikethrough option or Double Strikethrough option as you need, and click the OK button.

Now the selected text is formatted with strikethrough or double strikethrough.

You can clear the strikethrough or double strikethrough easily as follows:

1. Select the text with strikethrough or double strikethrough.

2. Click the Strikethrough button  in the Font group on the Format Text tab. (Tips: click the Strikethrough button twice to clear the double strikethrough).

Alternatively, you can untick both Strikethrough and Double Strikethrough options in the Font dialog to clear all strikethrough and double strikethrough formatting.