I second those asking what limitations you ran into (specifically with FastMail, since I have more chance of being able to fix those than the limitations with Protonmail - though I'd love to know both!)
If it's "costs money", we're not planning to change that! We (FastMail) are proudly a paid-only service.
When I signed up in 2016 (I’m still a customer btw) it was a big pain to get my custom domain added after paying for an account. I had to contact support for assistance. I somehow have to have two accounts for my plan but only one has a mailbox. Crazy bad experience here.
The amount of space we get for mail is low for the fee. I pay around $12/year in additional fees with Google for another 70GB of space outside of the 30GB they give for the base plan. Fastmail was pricier last I checked.
There is zero quality collaboration option for me. Even if you added one the fact that anyone who wants to collaborate would have to have a paid account with me creates a barrier for me to even try and use it for anything but just email.
The spam filter is about 30% as accurate as Gmail. I try and train it but don’t have time to always be doing that.
The mobile app on ios doesn’t remember me. It doesn’t even have an option to remember me. What a pain, I hardly even bother to use it because of that.
That all said. I like some things about fastmail:
The web interface is fast.
The admin features are robust and easy for adding aliases and new custom domains.
The fact you are pushing to make the world a better place for email is why I keep paying for the service.
What you are doing is hard. Your competitors are massive and well established. I hope you continue to make progress.
The biggest thing I've been missing since I started using FastMail is labels. My workflow in GMail used labels pretty heavily, and I've been able to get pretty close using saved searches and folders, but it's not quite the same.
Right, hopefully when JMAP arrives (soon!) you'll be able to use that nicely. It will give label-style handling by allowing the same message to exist in multiple folders.
Kinda hijacking this. When using FastMail with a custom domain can I setup a catch all address and then have each different address somehow tagged? It would be nice to be able to have proper unique email addresses for each service so I know where spam ends up coming from.
You can create an * alias in FastMail which will act as catch-all address. The received email will retain the original To: field so you can use rules to match them.
If it's "costs money", we're not planning to change that! We (FastMail) are proudly a paid-only service.