Hi @Richard,
Welcome to Microsoft Q&A, and thank you very much for reaching out to us.
Please note that our forum is a public platform, and we will modify your question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data.
Based on your descriptions, as I checked, kindly check the Deleted Items folder for your deleted email. If the email was permanently deleted, you can look in the Recoverable Items folder.
For more details, you can check on this Microsoft article here.
If the email still isn’t there, please contact your admin. They can use Microsoft Purview Content Search to locate the message, export it, and import it back to the mailbox.
It’s also worth checking whether there are any inbox rules that might be deleting emails automatically. You can do this in Outlook by going to File > Manage Rules & Alerts.
I hope this help. If you have any updates or concern, feel free to let me know. I would love to assist you further.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.