As you [should] already know, Gmail and Yahoo are taking additional steps to improve deliverability and block unwanted messages from user's inboxes. (We expect more providers to follow). There are new requirements if you want to get your emails delivered.
This site is a 3 step guide with some tools to help you be compliant.
Not really. Even though some of the rules are targeted at bulk senders, all senders are required to comply with others like authentication and spam. It is also in your best interest to comply for improved deliverability.
You are a bulk sender if you send more than 5,000 emails in a day. Hold on...even if you don't do that daily volume yet, remember you are planning to get there. Plus there will be special days when you will have to engage more audience than usual.
You get marked as spam? 🌚 And that's probably the best case scenario. Your email may not get delivered.