Dedicated or shared IP address with an SMTP relay: when to choose which?
For most companies a shared IP address is the better choice: it already has a reputation, the combined volume of many senders keeps that reputation stable, and there is nothing for you to warm up. A dedicated address only pays off when you send large, regular volumes, want the reputation entirely in your own hands and are prepared to build and watch it yourself. Take a dedicated address with a small or irregular volume and you get worse delivery than on a well-managed shared pool.
What an IP address has to do with delivery
Receiving mail servers keep a reputation per sending IP address, alongside that of your domain. An address that consistently sends good mail, with few bounces and few complaints, is trusted. An address without history is suspect. An address with a bad history is throttled or refused. So the question is: whose history does the address your mail leaves from carry?
Shared: the pool's reputation
On a shared address, or a pool of addresses, your mail leaves alongside that of the relay's other customers. The reputation is an average of everyone. That sounds risky, but in practice it is an advantage, provided the relay watches its pool:
- The address already has a history. Your first message leaves with trust, without a warm-up period.
- The volume is large and constant, even if you send nothing for a month. Reputation fades with silence; on a pool that does not happen.
- A badly performing customer is throttled or removed by the operator, so the rest are unaffected.
- A randomised pool with rate limiting per domain spreads the risk and stops one sender dominating the pool.
The drawback: you share the consequences when things go wrong and the operator does not step in. So the question is not "shared or not" but "how well is the pool managed". A relay that follows every customer, includes warm-up and personal follow-up and intervenes quickly delivers, on a shared pool, better than most dedicated addresses manage. More about how that foundation works is on the SMTP relay page.
Dedicated: your own history
On a dedicated address only your mail leaves from that address. The reputation is entirely yours: good if you do well, bad if you do badly. That is attractive for anyone who:
- sends large volumes, in the order of many tens of thousands of messages a month or more, and regularly;
- has a very steady flow, so the address never goes quiet;
- has strict requirements about who sends alongside them, for contractual reasons for instance;
- has the time and the discipline to warm up and monitor the address.
The drawback is exactly the flip side. A new dedicated address starts without reputation and has to be warmed up gradually over weeks, starting with your most engaged recipients. Send irregularly and the reputation sags between two sends. And every mistake, an old list, a campaign that draws complaints, lands entirely on your account, with no one else's volume to soften the blow.
The decision in three questions
- How much do you send, and how regularly? Small or irregular: shared. Large and daily: a dedicated address becomes worth considering.
- How good is your list? If you have doubts about your bounces and complaints, you are better off on a pool that limits the damage, and you work on the list first.
- Do you want to manage it? A dedicated address is a responsibility: follow the figures, respond to signals, plan warm-up. If nobody is available for that, choose shared.
A middle way: separate by type of mail
Often the real question is not which address, but which separation. Order confirmations and invoices do not belong on the same path as a newsletter that sometimes draws complaints. You arrange that with a separate sending subdomain and a separate login per type of mail, regardless of whether the address is shared. Transactional mail then keeps its reputation, whatever happens to the campaign. Why that separation pays off so much is on the transactional email page.
What we see in practice
A webshop with a few thousand order emails a month asks for a dedicated address because it sounds "more professional". On a dedicated address that volume would be too small to carry a stable reputation; on the shared pool it arrives fine straight away. A publisher sending tens of thousands of messages daily, with a clean list and a team that follows the figures, is a genuine candidate for a dedicated address. If in doubt, discuss your volume and your list with us; the choice depends on your situation, not on a rule of thumb.
Frequently asked questions
Is a dedicated address always better for delivery?
No. Without sufficient and regular volume a dedicated address performs worse than a well-managed shared pool.
Can I switch later?
Yes. Whoever starts on a pool and grows can move to a dedicated address later, with a warm-up planned around the existing list and figures.
Does a dedicated address protect me from other people's mistakes?
Yes, but it does not protect you from your own, and those then weigh more heavily.