How one customer used Fastmail’s Open API

Fastmail’s open API makes creating new and exciting tools easy for email enthusiasts.

Learn how Žymantas Paulas, a principal software engineer, used Fastmail’s open Masked Email API to create a new app for Fastmail users who use Masked Email extensively, called Secret Inbox.

What inspired you to start using Fastmail?

I have been actively using Fastmail for almost ten years now, since 2013. My privacy was the primary reason I moved from Google Apps to Fastmail. Also, I have always loved how fast the web version of Fastmail is. Although I use it quite rarely, every time I open it, I am repeatedly impressed by how fast it is.

Another thing that I have been impressed with was Fastmail customer support. Although I needed help just a couple of times over those 10 years, the response time and depth are something that any other company should be aiming for.

Do you use Fastmail for business or personal use?

I use Fastmail for both business and personal use. Some of the features I get the most use out of are:

  • I use mail filters extensively. Everything from uninteresting emails to my server notifications goes to different Folders.
  • I really appreciate server-side filters, as I use a different service for my domain, and Gmail did not provide those.
  • I love using different domains and aliases within a single account. I use a couple of other domains for various purposes.
  • I use Calendar specifically for my freelancing work-related tasks and meetings.
  • The home page of Secret Inbox is hosted at Fastmail as a static page.

What does Secret Inbox do?

The Secret Inbox gives people quick and easy access to their Masked Email addresses. If you use Secret Inbox on macOS, it’s easy to copy->paste a Masked Email using global shortcuts. I use either ⌃+ ⌥+⌘+n (creates new copies) or ⌃+ ⌥+⌘+n (copies the last one) to quickly access each Masked Email. The iOS is slightly different: it’s either a widget or a shortcut app. Also, “Hey Siri, copy Masked Email” works on both platforms!

Browser extensions that integrate well with the Safari browser on iOS are coming soon.

How was your experience working with Fastmail to get your API set up?

Funny story: after Fastmail announced Masked Email and their partnership with 1Password, I quickly looked into it to see if I could build something for myself. So, I created an API project and tried to set up everything.

At first, the Masked Email API wasn’t available to the public, but a year or so later, I learned that the Masked Email API was now available. So, I opened my API project and entered my API key, and voila. It worked! I was able to guess the correct API. I’d say the API was straightforward, even without the documentation.

Last but not least, email exchanges between Joe Woods and myself were always pleasant and helpful 🙂

What inspired you to build Secret Inbox?

I wanted to have an app that always sits in the menu bar of macOS or has a widget on iOS that allows me to create and use a Masked Email easily without opening the browser. So, I can press ⌃+ ⌥+⌘+n (user can define any shortcut) any time and paste that email where I want to.

Plus, all the other actions, like disabling, enabling, and deleting a Masked Email, are way easier and faster. If I start getting spam to one of my Masked Email addresses, I can disable it and forget it quickly.


Fastmail is working to make email better for everyone. We are committed to fostering a culture of collaboration by welcoming engineers like Žymantas Paulas to use our publicly available application programming interfaces (the “APIs”). If you are interested in building something using our API, check out our guide to getting started integrating with Fastmail.

We look forward to seeing what you can build with Fastmail!

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