In the early days of communication studies, there was a communication style known as Magic Bullet Theory or Hypodermic Needle Theory. According to this theory, if you send a message to your audience, you can assume that they received and understood it. Essentially, the message is the "bullet" and it's magic because it hits its mark every time.
You already know how I feel about assuming.
Although this theory has been disproved multiple times over the years, many organizations still use this communication style. Consider the common example of the "System outage" e-mail. The IT department needs to take down a computer system for maintenance, so they send out a mass e-mail letting everyone know that the system will be unavailable between 10 pm and 11 pm on Friday night. With that one e-mail, the entire communication plan is complete.
On Friday night, the IT team performs the system maintenance.
Inevitably, on Monday morning, there will be at least one e-mail...