Using classic Outlook for Windows in business environments
Hi, I'm Diane and I'm happy to help you today.
Your medstar account is using Microsoft 365 - your admin can run a message trace in the Exchange portal. The trace will show if it was handed off the consumer side but may not show what happened to it. https://learn.microsoft.com/Exchange/monitoring/trace-an-email-message/message-trace-modern-eac
Did the outlook.com user check the junk email folder? Add your address to their safe list? If the message was sent recently, the Outlook user can ask outlook.com support to trace. How to get support for Outlook.com https://support.office.com/article/f5482a98-616c-4d44-b7c5-8aaaadf5c11a
So there is no misunderstanding, please note that this is a public forum. We do not work for Microsoft and do not have access to user accounts.
Let me know how it goes, I'm here to help you further if needed.
-- Diane