I still don't get it; let's say I have 100+ signups a day on trial accounts and 200k+ paying clients which almost never receive email from us, but do sometimes

I still don't get it; let's say I have 100+ signups a day on trial accounts and 200k+ paying clients which almost never receive email from us, but do sometimes (maybe 1-2 times every few months). What are we looking at?