Do you mean you import your emls on DT and then make links for the reminders when you’re on DTTG?
It’s not possible to import emails into DTTG, is it? Or to export one or more messages from iOS Mail into DTTG?
I’ve just set up a system (with plenty of help from this forum) of ToDos using a Group per item, which contains a markdown file to track progress and make notes, emails, PDFs, and other related files that pertain to the task. The iOS Reminder links to the markdown file.
I have a smart template for DT and a shortcut for DTTG that both do the same thing.
That thread is here