Examples

1. Mary creates a message and addresses it to uwofficial-all@lists.wisc.edu and uwofficial-colleges@lists.wisc.edu. The message goes to both lists. If Bob is on both email lists, he will get the message once. M365 recognizes it's a single message and only displays one of them.
2. Mary creates a message and addresses it to uwofficial-all@lists.wisc.edu, waits 5 minutes, and then sends it to uwofficial-colleges@lists.wisc.edu. The message goes to both lists. If Bob is on both email lists, he will get the message twice. M365 recognizes it as two distinct messages and displays both of them.