Hi @Graham Fischer-Corners
Have you checked email in this public folder on OWA?
Please try to create a new public folder and enable the email. Then try to send a test email to it and see if it can be received normally.
Please try to run the following command move public folder mailbox where the public folder is located to a new database, then try to send a test email to it again.
New-MoveRequest -Identity <> -TargetDatabase <>
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