How do I make Mimestream the default email client?

Unfortunately, Mimestream cannot offer an option to become the default email client within the app. Mimestream is a “sandboxed” application (intended to be distributed via the App Store), and Apple’s macOS security restrictions currently prevent sandboxed applications from changing the default email client.

However, there are two methods you can use to make Mimestream the default email client, detailed below:

Using Microsoft’s SetDefaultMailApp tool

Download Microsoft’s SetDefaultMailApp tool and open it. Once the tool is running, you can set com.mimestream.Mimestream as the default email client.

Using Apple Mail

Open Apple Mail to change the default email client, following the instructions on Apple’s support site. However, if you’ve never used Mail before, you will first have to add an account because you can access the app’s preferences.