Hello KerryStretton,
Thanks for your post in Microsoft community. Regarding your issue, suggest you to check your sent items and verify if any mails found which was send to that unknown user account
belongs from exdigy.net. If mails are found in your sent items which were never send by you, please reset your password to keep your account safe.
Kindly provide us
Complete Non Delivery report (bounce back message ) as an attachment
and message trace details via
the Private Message.
- For message trace details: Login with Global Admin account in Microsoft 365 portal -> Exchange admin center -> Mail Flow -> Message trace -> add the sender (your email id) , recipient email
ids and select the date range (once message trace report open, select the trace, open it and share all the detail information). With message trace details, check if the mail originated IP is belongs to you or not.
For your privacy, we will send you private message for collecting it.
Thanks and regards,
Ankita Vaidya