Hey folks, thanks again for reporting this and I’m sorry for the hassle. I’m updating a lot of the CI workflows because our build provider Travis CI has stopped supporting macOS.
The download link for the fix is:
https://github.com/Foundry376/Mailspring/releases/download/1.16.0/Mailspring.zip
I’ve also updated our build process to sanity check this in the future via
file ./Downloads/Mailspring.app/**/* | grep "Mach-O"