Hey there,  @Gunni!  Thanks for reaching out in community - we’d love to help!
Can you elaborate a bit more on which apps you’re using for emails and accounting? That may help us give us a better idea of recommendations. Here’s a list of some of the more common email and accounting apps.Â
If you’re using Gmail though I wonder if this workflow will help:
Full transparency, this will likely require a paid plan though as it will require multiple steps and a filter step. Let us know if you think that will work though!