You are correct that there is not an email notification. The reason why is that there are many legitimate tines, such as for debug builds, where for many apps, they choose not to enable Crashlytics and in this case an email notification could easily get overwhelming. It's one of the reasons why we opted for an in dashboard alert.
If you want to automate dSYM uploads, I'd recommend looking at this blog post which would need slight modifications for using Firebase Crashlytics: https://krausefx.com/blog/download-dsym-symbolication-files-from-itunes-connect-for-bitcode-ios-apps
-Mike