Error at sending and cant find the mail in the outbox?

i sent a mail with wrong mail addresses in the CC, and it failed to be sent.

the main problem, is i got the below error more than 100 times, every 5 mins it popup. when i opened the outbox folder it is empty and i keep receiving this message and i can’t make it stop. and i cant find the mail in outbox to delete it

[Exchange Web Services] Sending email failed due to the following error: At least one recipient is not valid., Recipient ‘‘’’ is not resolved. All recipients must be resolved before a message can be submitted.

If they are not visible, enable Local Folders by selecting Menu > Settings > General > General > Show Local Folders.

Then go to the Local Folder Outbox and delete the message.