What are the pros and cons of shared IPs?

Shared IPs pool multiple senders onto the same IP address. Your reputation becomes intertwined with others on the same pool, for better or worse.

Pros: no warmup required since the IP already has established sending history. Lower cost because the infrastructure is shared. Ideal for smaller senders who lack the volume to sustain a dedicated IP's reputation. The ESP manages IP health so you don't have to.

Cons: bad behavior from other senders on the pool can damage your deliverability. You have limited control over sending patterns and timing. Troubleshooting becomes harder because reputation issues may not originate from your campaigns.

Think of it as booking passage on a cargo ship. You share the voyage with other merchants. If one loads contraband, the whole vessel gets inspected at port.