With all of the online platforms available it can be a misconception that you own all of the content you put out on social media and your website. But, truth be told if your website were to go down or your social media account deactivated. You will want that information you’ve been storing on those sites.
The best idea is to backup all your files and have copies off of all the online platforms. I do this with a 2TB EXTERNAL HARD DRIVE made by Western Digital.
I also use Google One more specifically Google Sheets - https://www.google.com/sheets/about/ (similar to Excel spreadsheets) to keep a list of my contacts and email list data. With spreadsheets you can collect and compile data about your audience. Google allows for up to 15 GB of storage and then you have to upgrade a GOOGLE ONE PLAN.
Eventually you will see the value of having a CRM software (Client Relationship Management) to store your data and manage it. HUBSPOT CRM (https://www.hubspot.com/products/crm) is a FREE database for you to store your contacts. They offer email service and other marketing options for a fee. If you have ever used Salesforce or heard of it this is an alternative.
While Hubspot does have email marketing services. I started out using Mailchimp (https://mailchimp.com/) to handle my email list and newsletters. Mailchimp is an email service provider. Usually free to start up to the first 2000 subscribers. User friendly and easy to set up.
Now, I use Active Campaign for most of my email marketing services and they also have other features such as CRM database management as well. Personally I prefer the options Active Campaign offers although it does take some time to play with and get use to. It is a beast once you learn how to use it.