Reason 1: Interference with the Outlook application by third-party software.
Reason 2: Inappropriate or incorrect server settings in Roadrunner on Outlook.
Reason 3: The 'Working Offline' Mode in Outlook may be enabled.
Reason 4: Check the filter settings on your Roadrunner account.
Reason 5: Double-check the file's email space, size, and format.
Reason 6: Incorrect or obliterated password.
Reason 7: Roadrunner isn't set up correctly in Outlook.
If you are unable to resolve the issue, you can contact for professional assistance.
I hope this answer helps you.