I like that it lets me know when my email is opened or read in real time so this helps to keep track of how many people are actually reading each one! It's easy for others who work at our office as well too see what we're working through/on right now which makes collaborating much easier than if they were just going off their own thoughts only (which can be difficult). There isn't anything really bad about mail warm but maybe more options would help? Maybe make them look different from all other folders you have set up within outlook depending upon where its been sent out instead perhaps?? As long there aren’t any issues i don;' t think anyone will mind using mw because everyone wants better open rates!! We've noticed an increase since implementing mailbox warming into some campaigns compared before implementation- definitely beneficial overall.