These are the tools I use and recommend:
Active Campaign - This is my email marketing platform of choice. I use it for a number of email lists/businesses and it's also the tool that drives my membership websites. What I love about Active Campaign is their automation tool and tagging system.
So contacts can be tagged based upon any number of reasons and then automations can run based on the tags, or even add/remove tags themself.
So say you click on a link in an email that says "tell me more" about a topic. That email could tag the contact which triggers a series of emails all about the topic they're interested in.
That is a very very simple example.
However, if you need a simple email marketing tool that still packs power then Mailchimp is a great starter. I used them when first starting out as they offer a free tier.
Social Bee - A social media management tool that lets you build a categorised content library. You can then choose how often and how many times each category posts. Once the queue is empty Social Bee will start from the beginning and repost. Visit their website to sign up.