Email is still among the most valuable communication tools. There are external influences reflecting the downturn in open rates, however as long as your content is valuable you should continue to send them out. Value is the key. Listen to your audience by the numbers and conversations you have, gear your content strategy to meet their needs.
Also, your unsubscribe rates are really important, it helps you understand your true audience. People have time to clear out their inbox, so don’t be too disheartened when your numbers start to decline.
Overall, don’t do the hard sell and keep it relevant and true to your brand.