Sometimes emails that are sent from you are actually sent by a different person and redirected as if it were coming from you. To determine the cause:

1. Check all email accounts associated with the email address sender.
2. Check the email headers to find out from which server the email was sent.
3. Contact the webmaster or IT department of the domain for any suspicious emails sent from the domain.
4. Check for spam emails sent from the domain.
5. Check for email viruses or malware software in the email accounts.