Hello,
I'd like to help you on this! I understand the issue is you need a way to bulk-flag incorrect (bounced) addresses so that they can later be checked by staff and corrected/removed.
I can implement this in multiple ways, either by adding a bit flag next to the email address - in your database - which would be the technically preferred way or if - as I think - this may possibly adversely affect your application, we may also use the original way you suggested, i.e. prepend the address with a predefined text that indicates incorrectness/need to check.
I will: write a .net application that allows you to configure this above message and paste a list of email addresses (as a text file, one address per line or separated by a semicolon) and it will look at and amend any matches as described in the project bid request. Prior to getting down to developing anything I would like to quickly discuss the specifics with you in order to make sure we grasp every aspect and pick the most optimal solution.
You will receive complete IP rights, a Visual Studio 2013 solution with the app developed using .net framework 4.5 and C# as programming language as well as robust, tested, working and commented code. In addition, I will be available later for any enhancements you may require.
I look forward to working with you. If you have any questions just PM me via the site!
regards,
Janos