Why is it important to warm up a mailbox, domain, and IP?

Posted by Iam_feysal@reddit | sysadmin | View on Reddit | 232 comments

Setting up a new mail server for a client and they're planning a big email marketing push on day one. I told them we need to warm up the IP and domain first but they're pushing back, saying it's a waste of time. What are the actual technical consequences if we just start sending out 10k emails from a cold IP? I need some ammo here lol.