Let's take the low side on this: 20,000 emails over a two-year period equals 27.4 emails a day. Assuming a two-way conversation, that's 13.7 each, per day, for two years. Who are these people? The leaders of the free world or 13-year-old children? And haven't they ever heard of
sexting texting? You can generally find a free plan in such high-volume instances.