What is Dedicated sending IP?
An IP address used only by your mail, so your reputation isn't shared with other senders on the same infrastructure.
Hosted mailboxes send through their provider's shared IP pools, where another customer's bad behaviour can affect your placement. A dedicated IP isolates you: its reputation is yours alone to build and keep. It matters most at higher volume; below a few thousand emails a day, mailbox and domain reputation dominate. A dedicated IP also needs warming, like a mailbox.