Smart Compose operates in the background, letting you accept its suggestions or ignore them, so you don't need to change the way you currently compose drafts. When you see a suggestion you like, you can simply hit the tab button to accept it. It works for your greeting and closing, as well as common phrases in between.
It has the added benefit of potentially reducing grammatical and spelling errors. Whether anyone uses it or not is another question, however -- I can't say I've ever added Gmail's Smart Replies, for instance, as they're too impersonal for most situations. Smart Compose's suggested greetings and closings might be handy, though.
Either way, Smart Compose will appear in the new Gmail for consumers over the next few weeks, and arrive to business G Suite customers in the coming months.
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