When you’re employed by the state to shit post as your day job, I imagine you have numerous tools — an entire web platform to efficiently orchestrate and coordinate your activity — and time to post everywhere. Strategically, Lemmy is a low investment and could potentially lead to dominating and moderating a much larger community in future.
As others suggested you don’t need all your historic mail on your mailserver. My approach to email archival is the same as all my historic data — a disorganized dumping ground that’s like my personal data lake, and separate service(s) to crawl, index, and search it (e.g. https://www.recoll.org/)