If it appears that someone is sending spam from your email address, there are two possibilities. One is that your email account password has become compromised and used to send spam. Typically when this happens you'll receive notices from the server in the form of bounce messages indicating that you have reached your maximum number of emails per day, or that you've reach your maximum deferred or bounce message per hour. In this case, you should follow the instructions to change your email password.
Alternatively, the problem may be that your email address is being forged. In this case, we recommend opening a support ticket so we can review your SPF, DKIM, and DMARC records to ensure your domain's sending policies are set correctly.