Hi, @Royal D Costa
Did the senders receive NDR messages indicating the mail delivery failure?
If they didn't receive any NDR messages, and the message tracking log shows the mails are delivered, you may use the search-mailbox command to check if the mails are in the users' mailboxes.
For example, the following command searches mails which contain "test" in the subjects in userA's mailbox and export the search results to the inbox of the administrator's mailbox. ( Don't forget to add -LogOnly otherwise the command will copy the mails to the target folder)
Search-Mailbox -Identity "userA" -SearchQuery 'Subject:"test"' -TargetMailbox "administrator" -TargetFolder "inbox" -LogOnly -LogLevel Full
From the "Search Results" csv file, you may see the folder which contains the mails.
If you can't find the mails in message tracking log, were the mails sent 30 days ago?(by default, message tracking log is kept for 30 days)
And is it a stand-alone Exchange server or do you have other Exchange servers in your environment?
Please also confirm if the senders receive any NDR message for the mail delivery failure.
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