Dedicated or shared IPs: the volume question

The pitch for a dedicated IP is control: your reputation, unaffected by anyone else. The pitch is true and incomplete, because reputation requires volume to establish and a dedicated IP with no volume has none.

How each actually behaves

Shared. You send from a pool used by many senders. The pool has an established reputation, so your first message benefits from history you did not build. You also inherit whatever the worst sender in the pool does this week.

Dedicated. The IP is yours. Your reputation is yours alone — which on day one means no reputation at all, and unknown is treated closer to bad than to good.

The threshold

The number usually cited is around 50,000 messages a month as the floor for a dedicated IP, and the reasoning matters more than the figure.

Reputation is built from consistent, recent sending. A provider scoring an IP wants recent history. An IP that sends two thousand messages in a month, in bursts, never accumulates enough signal for a confident judgement — so it stays unknown, and unknown mail is filtered more aggressively than mail from a known-good shared pool.

It is not only the total. Consistency matters as much. A hundred thousand messages a month sent evenly builds reputation; the same hundred thousand sent on two days a month does not, and the quiet weeks let what you built decay.

When dedicated is right

• Sustained volume above the threshold, sent regularly rather than in bursts
• Mail whose delivery you cannot afford to have affected by strangers — payment confirmations, security alerts
• A compliance requirement to demonstrate the sending path
• You are large enough that a shared pool's worst sender is a real risk

When shared is right

• Below the threshold, or bursty
• Early-stage, where a provider's established pool is worth more than independence
• Nobody available to monitor and warm an IP properly

There is no shame in shared. A well-run pool outperforms a badly warmed dedicated IP by a wide margin.

Switching

Moving to a dedicated IP means starting from zero, so it is a warmup, not a cutover. Send your most engaged recipients first, keep the rest on shared, and shift volume over weeks.

Do not move everything at once. A new IP that suddenly sends your full volume looks exactly like a compromised host, and will be treated as one.

The middle option

Several dedicated IPs in a pool, with messages distributed across them, is standard above a certain scale — it spreads per-IP rate limits and means one IP getting listed does not stop everything.

The trap is doing it too early. Four IPs each sending a quarter of your volume is four IPs each below the threshold, which is worse than one IP above it.