0x80040109 - The Operation cannot be performed because the message has been changed

Error Message -

Task 'pop.bluetie.com - Sending' reported error (0x80040109) : 'The
operation cannot be performed because the message has been changed.'

Troubleshooting -

1) Disable email scanning and then restart Outlook

2) Check for any add-ins that may have altered the message by going to

Tools -> Options -> Other -> Advanced Options... -> Add-In Manager...