There has been discussion from time-to-time of integrating with an email client for those switching from Microsoft Office, who now lack Outlook.
Thunderbird has often been the client discussed. I would like to see integration with Spicebird, which is built upon Thunderbird, and surpasses it in many ways.
For integration, I'd like to see email links within the suite pull up Spicebird, linking help files, and a visual theme for Spicebird to provide a consistent looking UI. The spellcheck dictionaries can be shared, and perhaps even further integration would be possible down the road.