Preventing spam is a lot easier than it was a decade ago. The software is far better, and there are now things like SPF records that make it much easier. Email on Portal is a very basic Dovecot+Postfix server with Roundcube for webmail. It's not as good as Gmail but it works quite well.
Not so long from now we'll have something better than Gmail. There are a lot more developers outside of the Gmail team than inside of it. What's been missing is a platform for them to develop on.
DigitalOcean has "one-click" apps but they're really just installers that can be run once. Configuration and upgrades are completely manual after the first step. You still have to be a sysadmin to do almost anything. Portal doesn't require any sysadmin tinkering. Upgrades and configuration are automatic.
Every Portal app runs in a separate VM and they're are all mapped to your domain name. Every user has an SSL certificate and a dedicated IP address. Completely non-technical people can use it to run the kinds of things that only hackers run today.
We would like to see a world where companies like Automattic support self-hosted versions of their products. Kind of like desktop software companies support paid version of their products. That's not the case today, but there's no reason people in the future can't run their own server software, and have it be very reliable and 100% supported by the app developer.
Also, although I'm a web-dev and have "insights" on most of the tech news/trends I would never recommend to host a blog on your own VM. It would be much better if it's a paid hosting service, specialised let's say in WordPress, than having this on your own VM shared with your e-mail service.
And what is your main difference, between having a DigitalOcean + Installed app versus Portal?