What is a shared IP address for email sending?

Shared IPs are used by multiple senders. Your emails go out alongside other customers of your ESP. You share the IP's reputation with everyone using it.

Dedicated IPs are exclusively yours. Only your emails come from that address. Your reputation is solely determined by your sending behavior.

Shared IP advantages:

Established reputation from day one (if the pool is well-managed)
No warm-up period required
Lower cost, often included in ESP pricing
Good for lower-volume senders

Shared IP risks:

Other senders' bad behavior affects you
Less control over reputation
One bad actor can tank deliverability for everyone

Dedicated IP advantages:

Complete control over your reputation
Isolation from other senders' mistakes
Easier to diagnose and fix issues
Better for high-volume senders

Dedicated IP requirements:

Sufficient volume (typically 100k+ monthly) to maintain reputation
Warm-up period needed before sending at full volume
Higher cost
More responsibility for reputation management

Shared IPs are like a cruise ship: convenient, but you're at the mercy of your fellow passengers. Dedicated IPs are your own vessel: more work, but the course is yours to chart.