unauthorized email Forwarding

Hello Tom. If your Junk folder is filling up with bounced forwarded emails you did not send, it is likely that your account credentials were compromised and someone was able to send spam using your account as an identity, via some third-party service(s) or app(s). Because these messages will not appear in your Sent folder and your settings in Outlook show no forwarding rules, the activity is happening outside of the Outlook client and is perhaps the result of a vulnerability which would give someone access to your account through IMAP or SMTP.

To address this issue:

1. First, change your Microsoft account password immediately and enable two-factor authentication to lessen further unauthorized accesses.
2. Next, review your account's recent activity Microsoft security page to see if there were suspicious logins or app connections made.
3. In Outlook, go to Settings > Mail > Forwarding and ensure no sneaky rules have been established or forwarding addresses are active.
4. In your Microsoft account, check Connected Apps and Services to revoke any app connections that are unacceptable.
5. If you are using Legacy Outlook for Mac, it may be a good idea to consider transitioning to the modern Outlook version which has better support and security.

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Best regards,