If we want to emphasize something or express urgency, you and me will immediately think of adding an exclamation mark. But exclamation marks do not metaphysically put importance in the words preceding them, they just express the importance that's already there (or can only be heard, as in the command: "Go!").
That's why it is a good idea
- not to use exclamation marks at all
in your email marketing copy. If you feel the need to use an exclamation point, reread and reword the sentence (or the whole paragraph) to make the words, the rhythm and the sentence structure develop their own urgency and importance.