Hi @EsthThala ,
This may be an email sent by another group to this group. The user is in the group, so he will receive it. Please confirm whether other members of this group have received it.
If not, you can try removing the user from the group and adding it again to see if the problem is resolved.
This also could be happening because the Microsoft 365 group is set to allow external senders to email the group, and the user's email address is being included in the email messages. To resolve this issue, the group owner or tenant admin needs to disable the " Let people outside the organization email the group" setting for the Microsoft 365 group.
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