Nope, it is just not built like that. If you can work with the associations, as suggested by Shreyash, you will be fine.
If not, you have several options:
- Create a helper-entity, 1-* associated with each of your two entities; pass the helper-entity to your mail-template, and use the association to get the attributes in the mail; This is probably the most straightforward solution;
- Prepare the data that you need in your mail in a separate helper-entity, that contains all attributes and their values for this specific email;
- Replace the module with Marketplace module EmailService, where you prep the contents in the microflow itself. No hassle, no templates. In my not very objective opinion (I wrote the module), this is by far the best solution.
You’ll probably go with 1)
Have a nice day