Hi @Brooklyn.Slone ,
Welcome to Microsoft Q&A and posting with the "Outlook" tag which is for questions related to the Outlook desktop client.
From your description, could you please provide some more details as listed below so that we can understand better about your situation?
- Does the issue only occur when you try to send to the specific family member? Are you able to send mails to others successfully?
- How does the bounce back rejection email notification look like? If possible, you can remove all personal information and share the details or a screenshot of the bounce back message.
- What's the type of your email account? Is it a personal outlook.com account?
Besides, to help narrow down if it's an issue with the Outlook client, please try sending a test message via the web mail instead and check the result.
In addition, if it's currently only happening when you send to some particular recipients, you can also try asking the recipients to add your email address into their safe sender list and see if there would be any improvement.
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