Below are some tips to help prevent your emails from sending multiple copies of the same message:

1. Check the number of recipients you selected – if they are more than one, confirm the list is correct.
2. Ensure all recipients have not been typed in by hand – automated tools like Outlook's ‘insert contact’ option should be used to add contacts to your email.
3. Check to see if email alias names have been used – contact alias names often result in multiple copies of the same email being delivered.
4. Check to see if any distribution accounts have been used – Distribution accounts will send emails to all members of the account, resulting in multiple copies of the same email.
5. Check to see if the same contact is added multiple times – ensure the same contact has not been added multiple times to the recipients list.