Shared vs dedicated IPs

A dedicated IP carries one sender's mail and one sender's reputation; a shared IP carries many senders' mail under a pooled reputation. Shared IPs suit low or irregular volume, where no single sender could sustain a reputation alone, at the price of inheriting poolmates' behavior. Dedicated IPs give high-volume senders full control of, and full responsibility for, their own reputation, and they need warmup before carrying real volume.