Finally I was able to solve this via GeometryProxy with some math. It could be hard to wrap the brain around local and global coordinates relationship.

I did several times a clean build. My development machine is a MacBook Pro M1 on Monterey and therefore I cannot use Xcode 12 anymore. I wan to copy just the application to the older Mac and not use Xcode on that machine. The test project was also created on my development machine. Any yes: The error message is really strange.

Meanwhile I got it working. Now I use SwiftSMTP which works well in background. See “swift-smtp/Sources/SwiftSMTPCLI/main.swift“ for sample code how to use it.