If you have a list in the body of a message you're composing, you can have Outlook sort that list for you, either from A to Z or Z to A.
- Select the text in a one-level bulleted or numbered list.
- Go to Format Text > Sort.
- Set Sort by to Paragraphs and Text in the Sort Text box.
- Select either Ascending (A to Z) or Descending (Z to A).
- Select OK.
For info on sort options, see Sort dialog box.