We have a major update coming out this month that will greatly improve the quality of our digests as well as the number of communities on outposts (2k -> ~8k communities). So we are hoping this improvement in digest quality will help. 
We also have plans for onboarding more community admins on to outposts so they can better amange their community news being distributed through the newsletter. With this we'd hope to see more of a push from communities to get their users staying up to date with projects through outposts. 