Hello gatoritz,
Thanks for using Apple Support Communities.
I see from your post that you're not seeing any Spotlight search results for the Mail app. Please make sure you have Mail enabled for the Spotlight Search by going into your settings shown below.
Go to Settings > General > Spotlight Search.
From here, you can turn Siri Suggestions on or off and choose which apps to include in your searches. For example, if you don’t want to see search results from your Messages app, you can deselect Messages.
Use Search on your iPhone, iPad, or iPod touch - Apple Support
Take care.