At the minimum, a prepositional phrase will begin with a preposition and end with a noun, pronoun, gerund, or clause, the "object" of the preposition. In = preposition; the, weedy, overgrown = modifiers; garden = noun.
The prince laid himself down on a couch with no pillows, he was upset and thought of what he has to do. He tries to get some food to eat but there were only rotten apples. There was a songbird with him and he takes out his anger on the little bird.
I'd say probably when the person you are contacting prefers communicating via call or text or another form of messaging. For almost anything professional or business related, it would be appropriate and acceptable to email.
