It depends on the situation. If, for example, you’re writing an email to one of your teammates or a millennial customer, adding a couple of fun GIFs to the message is a great way to lighten the mood.
However, if you’re crafting an internal email about the latest financial report, incorporating GIFs isn’t a smart idea as the topic is rather serious and you might come across as unprofessional. Before you add a GIF to an email of yours, ask yourself whether it will provide value to the message.