This is how Microsoft and other companies ended up setting servers on fire when Microsoft Exchange email servers were all the rage to run on prem. Think what happens when you have a company of 100k+ people and one idiot makes an email to a company wide distribution group. Then think about if someone replies, or two people reply, or ten! Soon your own company is bringing down their own email servers because of one improperly made distribution group. Think about how much of a mess that is to clean up on the back-end.