You can save your emails from being unsubscribed/trashed by adding a proper subscription-preferences option in your emails (works best at the time of signup). Giving subscribers the option to choose what they want to receive from you and decide how often (frequency of the emails) your emails should hit their inboxes will increase the reach of your campaigns manifolds. 

Before adding this option to your emails, consider the following points:

1. Don't ask too much information from your subscribers: Collect only details that help you offer a personalized experience for your subscribers like the type of content they want, time of the day they read emails, various topics that interest them, etc., and avoid getting any personal information. 
   
2. Make your subscription-preference option easily locatable: Help subscribers easily locate your preferences option so your email marketing efforts don't take a hit.  
   
3. Remember your mobile subscribers: More than 50% of your subscribers are likely to open emails on their mobile devices. So, it is important that both your email and the subscription preferences form are mobile friendly.
   
4. Add unsubscribe link (with a heavy heart, of course!): Yes, you like it or not, it is a good practice to include an unsubscribe link in your emails. It will let the uninterested subscribers opt out from your service, thereby improving the health of your mailing lists.