Shared vs Dedicated IP for Cold Email

The pitch for a dedicated IP is intuitive and almost entirely misleading. It goes: on a shared IP you are at the mercy of strangers, so pay a little more, get your own address, and your deliverability becomes your own business. Most senders who follow that reasoning make their placement worse, and it takes them a month or two to notice.

The reasoning fails because it treats an IP address as though it carries value by default. It does not. An IP address carries history, and a brand-new dedicated IP has none.

Why "no reputation" is worse than "shared reputation"

Mailbox providers decide what to do with your mail using evidence. A shared IP that has been sending clean traffic for years is dense with evidence: thousands of messages a day, consistent engagement, low complaints. When your mail arrives on that IP, it inherits the benefit of that record.

A fresh dedicated IP arrives with nothing. To a receiving filter, no history is not a neutral starting point — it is an unknown, and unknown senders are treated as risks. This is the same logic that makes a new domain harder to send from than an established one, and it applies to IPs just as directly.

So the real comparison is not "your reputation vs. strangers' reputation". It is "an established good reputation you share" vs. "an empty reputation you own". Below a certain volume, the first is simply worth more.

The threshold is about consistency, not size

The number people ask for is a volume threshold, and the honest answer is that consistency matters more than magnitude. A dedicated IP holds a reputation only if it sends regularly enough for receivers to keep forming an opinion. Long gaps let that opinion decay, and the next send is evaluated almost from scratch.

As a rough guide, consistent sending in the tens of thousands per month, every month, is where a dedicated IP becomes viable. Below that, you are unlikely to generate enough signal to build a reputation faster than it fades.

This is why bursty sending is such a poor fit for dedicated infrastructure. A team that sends nothing for three weeks and then pushes fifty thousand messages in two days has a high monthly volume and terrible reputation dynamics: every campaign looks like a sudden spike from a sender the network has half forgotten. That same pattern on well-managed shared infrastructure is absorbed by the pool's baseline traffic.

Reputation has largely moved to the domain

The IP-centric view of deliverability is a decade out of date. Modern filtering weights domain reputation far more heavily than IP reputation, for the straightforward reason that domains are harder to churn through than addresses. An abuser can rotate IPs cheaply; rotating domains costs money and time and leaves a visible trail.

This has a blunt practical consequence. If your domain reputation is damaged, changing IP does approximately nothing. Your From address is unchanged, your authentication still resolves to the same domain, and the filter's opinion of that domain travels with the mail. Teams routinely spend weeks and real money migrating to dedicated infrastructure to escape a problem that follows them across on the first send.

Before considering an IP change, it is worth confirming what is actually broken. Check whether the sending IP is on an authoritative blocklist. If it is clean, the IP is not your problem, and the answer is somewhere in your domain's history, your list quality or your content.

The question that actually matters

Framing this as shared-versus-dedicated hides the variable that does most of the work: who manages the pool.

A shared IP is only as good as the discipline of the provider running it. A well-managed pool enforces authentication on every sender, monitors complaint rates continuously, and removes senders who damage the neighbourhood quickly. A poorly-managed pool sells access to anyone and lets the reputation drift downward as its worst customers set the tone. Both are "shared IPs" and they are not comparable products.

So the useful questions to ask a provider are not about exclusivity. They are: what do you require of senders before they can use this pool, how do you detect a sender who is degrading it, and how fast do you remove them? A provider with clear answers is offering something better than most dedicated IPs. A provider without them is selling you the average of their worst customers.

A reasonable default

For most cold outreach programmes the sensible path is: start on well-managed shared infrastructure, put your effort into the things that actually move placement — authentication, warm-up, list quality, targeting — and revisit the IP question only when your volume becomes both large and regular.

If you do move, treat the dedicated IP exactly like a new domain. Ramp gradually over several weeks, watch your bounce and complaint rates at each step, and expect placement to be worse before it is better. The teams who are disappointed by dedicated IPs are almost always the ones who switched on a Friday and sent full volume on the Monday.

RepMail sends through AWS SES on managed, monitored infrastructure, with authentication published for your own verified domain and a progressive warm-up applied automatically to new senders. That combination gives a new sender the practical benefit people hope to buy with a dedicated IP — a clean, policed sending environment — without asking them to build an IP reputation they do not yet have the volume to sustain.