The Tip of the Night for December 19, 2019 discussed the categorization of different platforms' emoji pictures by the Unicode Consortium. There are subtle differences in the images that different platforms, Google, Apple, Windows, and others, use for emojis of the same type - grinning face, heart, dog, and so on.
An emoji entered on one platform by an email author may be seen differently by her recipient using a different platform. So, in this example the bomb emoji, with a rather long fuse, I entered in a new message using my gmail account:
. . . is received in my hotmail account as a bomb emoji with a fuse that is exploding.
As pointed out in Eric Goldman's study, Emojis and the Law, "Individual emojis often qualify for copyright and trademark protection (and possibly other forms of IP protection), discouraging rival platforms from making identical emoji depictions and driving cross-platform depiction diversity." Eric Goldman, Emojis and the Law, 93 Wash. L. Rev. 1227, 1230 (2018).