I work in marketing and only recently realised how closed the internet has become. I’ve always held that social media can come and go, people can use messenger and Twitter and Snapchat and insta all they like but email is a always a leveller that always works - then I found out about sending reputation. There’s a reason no one uses their own mail servers anymore, if you set up an email server on your own hardware then there’s a good chance that your emails won’t make it to the recipients behind spam filters. Basically, if you want to send emails now then you need to do it through an established service.