In the message editing window in Outlook, please follow below steps to add glow effects for the selected text in the message body.

1. In the message body, select the text you will add the glow effects for.

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 the Font dialog, please click the Text Effects button at the bottom-right corner.

4. Now in the Format Text Effects dialog, enable the Text Effects tab, and click the blank arrow  before Glow to expand this section.

5. Please configure the glow parameters as you need.

(1) Presets: Pick up one style of glows from the Presets drop-down list as you need.
If the chosen glow style can meet your needs, you can finish the configuration, and click the OK buttons to close both dialogs. If not, please go ahead to configure other options.

(2) Size: Drag the slider or enter a number of points in the Size button to set the glow size.

(3) Transparency: Drag the slider or enter a percentage in the Transparency box to set the glow transparency.

6. Click the OK buttons to close the Format Text Effects dialog and Font dialog successively.

So far, the specified glow has been added for the selected text in the message body.

If you need to remove glow effects from some text in the message body, please do as follows:

1. In the message body, select the text whose glow you will remove.

2. Press Ctrl + D keys to open the Font dialog, and then click the Text Effects button in the Font dialog.

3. In the Format Text Effects dialog, enable the Text Effects tab, and select None from the Presets drop-down list in the Glow section.

4. Click the OK buttons to save the changes and close dialogs.