Error Code: 0x800420C8
Similar Symptom:
Message Could Not Be Opened From Outbox Folder, Account:
(various SRX cases have the error code mislabelled at 0x800420C8)
Possible Cause:
This behavior can occur if you have two identical accounts with different names or the Outbox.dbx file is corrupted.
Resolution:
Delete and reset the email account in outlook and make sure there’s only one identical email.