Outlook remembers email addresses you have previously used and suggests them when you start typing a recipient.
If Outlook keeps suggesting an old or incorrect email address, you can remove it from the AutoComplete list.
Open Outlook and create a New Email.
Start typing the person's name or email address in the To field.
When the incorrect address appears in the suggestions, move your mouse over it.
Click the X next to the incorrect address.
You can also highlight the address using the keyboard and press Delete.
The incorrect address will be removed from the AutoComplete list.
The next time you email that person, type or select their correct email address.
If the Incorrect Address Comes Back
If you use Microsoft 365, Outlook may obtain recipient suggestions from Microsoft Search as well as its local AutoComplete list.
If the incorrect address keeps returning, check whether the person exists in your Outlook contacts with the old address and update or remove that contact.