Hi! If this account is happening on an Outlook account, please do this in Outlook.com:
- Sign in to Outlook.com
- Click the gear (Settings) in the upper-right corner.
- Search and enter mail settings.
- Go to the Rules section and check if there are rules you didn't create. If there are suspicious rules delete them immediately.
- Also check in Forwarding and IMAP and make sure that no address is added.