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error code 0x8007007A
I'm sorry that no satisfactory explanation of this error or resolution for it has been posted in this thread despite its age. This is most likely because the error is program-specific and independent of the operating system, so the question should have been asked in the program forum, not the one for a particular version of Windows. The original poster wasn't to know this, of course, but the moderators involved should have moved the question to the right place.
This error arises because you tried to send a message including a photo album. This feature no longer works as a result of changes at OneDrive, where the photo album would have been stored had the changes not taken place. This means that the message is now stuck in your outbox and may be preventing subsequent messages from being sent. The outbox is below the account folders in the folder pane:
Remove any unsent messages from the outbox, then compose a simple test message with a unique subject and send it to yourself. Post any new error message in your reply.
You'll find some alternative suggestions for sharing pictures in this article: Avoid 'photo email' and send photos by email
The error has nothing to do with the account being used to send messages, so removing and re-adding this account will have no effect on it. Nor will repairing the installation, which ensures that all the program files are present and correct. There's nothing in the error message to suggest that there was anything wrong with them in the first place.