Members of your Switchboard receive consistent communication around everything from new posts to requests to submit feedback, which inspires ~60% of the activity seen/measured on Switchboards.  So it's clear that consistently messaging the progress and value of your Switchboard encourages users to continually engage with your Switchboard, and that same impact can be made with newsletters to people in your community that are not on Switchboard yet.  Newsletters (especially e-newsletter) are low hanging fruit that can generate consistent growth that is integral to the sustainability of your Switchboard, and below are a few examples from which to draw inspiration.