To make it easier for users to search through the emails, I would add the ability to filter the given results. This would involve having, perhaps, a 'Filter' dropdown menu, allowing the user to filter the results by recipient, sender, subject, etc. The description of this challenge describes being able to retrieve and verify the emails of any concerning parties, but, without the ability to filter by email, this task would be long and tedious.
It may be beneficial for users to be able to see the attachments to any emails. This could be accomplished by displaying a popup when the paperclip/attachment symbol is hovered over, showing attachment names, file sizes, and file formats. Similarly, being able to hover over the badge that shows the number of additional recipients and see the list of email addresses could also be beneficial to users of this software.
My UI mockup only factors in two scenarios: less than or equal to 550 pixels in width, or greater than that. In order to be a more responsive app, additional scenarios should be considered. For example, a tablet may have trouble displaying the desktop layout as its screen is too small, but it may also have difficulty displaying the mobile layout nicely.
With longer email addresses, the columns can be too thin to display said addresses in full. This is very inconvenient. To fix this, I would add the ability to click and drag the column headings to make columns wider or narrower, or even the ability to change the font size so more text can be displayed at once.