Warm up a new IP or domain.

A new dedicated IP has no reputation. Mailbox providers treat it like a stranger at the door. This lesson covers why you ramp, what to send first, and how PostShiba holds a new IP to about 100 messages a day for two weeks.

Skip warm-up and providers push back. Try a blast on a cold IP below and watch deferrals climb.

Why reputation starts at zero

Mailbox providers score the IP that connects and the domain in the From address. A brand-new dedicated IP has never delivered to them. They have no reason to trust a sudden pile of mail from it. Send a small, wanted stream and grow it while the numbers stay clean.

Shared IPs are different. PostShiba keeps those warm with traffic from many senders, so a new sender on a shared cluster can deliver from the first message. Your domain still needs a history of its own. A cold domain on a warm IP can still get deferred.

Dedicated IPs are an add-on at $50 a month, bought from Network and attached through Sending IPs or an IP pool. Customer clusters stay on shared IPs until you add one. Stay shared under about 50,000 messages a month, or when volume comes in bursts. A dedicated IP that is busy one week and silent the next looks like a spammer.

IP reputation and domain reputation

IP reputation is the score on 198.51.100.10 or whichever address the capsule uses to talk to Gmail, Yahoo, or Outlook. Bounce it, complain about it, or go quiet, and the score drops.

Domain reputation is the score on mail.example.com. It moves with the From domain and the aligned return-path. It survives an IP change and follows you onto shared IPs. That is why SPF, DKIM, and DMARC have to be right before you warm anything.

If the domain already sends on shared IPs or another provider, it has a head start. The new IP does not. Ramp the IP anyway.

Send the mail people want first

Order the stream by how likely the recipient is to want it. Receipts, password resets, and replies from people who signed in this week teach a provider that the IP sends useful mail. A newsletter to a list you have not touched in six months teaches the opposite.

A working order:

1. People who signed in or bought this week. Receipts and replies first.
2. Recipients active in the last 60 days.
3. Recipients active in the last 90 days.
4. Your regular mix, once the early rows stay healthy.

Do not start with a re-engagement blast or a purchased list. Import your suppression list before the first send.

Ramp per provider

Gmail, Yahoo, and Outlook each keep their own view of you. Raise each provider on its own schedule. Hold a provider that pushes back while the others grow.

Keep your current provider, or the cluster's shared IPs, as the main path. Send a growing share through the dedicated IP or pool. Decide once per message and record the choice, so a retry never goes out twice.

Plan a ramp below, then compare it to the schedule most senders use.

The numbers are messages per day to each large provider through the new IP or pool.

Only move to the next row when the signals below look healthy. Go slower with a provider that pushes back. Most senders reach full volume in 3 to 6 weeks.

Signals to watch

PostShiba does not track opens or clicks. Watch what providers do with your mail: deferrals, bounces, and spam reports. Analytics groups by mx_provider and sending_ip.

Divide each count by processed, provider by provider.

A day with 400 processed at Yahoo and 31 deferred is not a green light. Deferrals are almost 8%. Hold Yahoo. Let Gmail keep growing.

Check this every day of the ramp, before you raise a provider's share.

When deferrals rise

A deferral means the receiving server asked PostShiba to try again later. Delivery continues. A rising rate means that provider has seen enough from this IP for now.

Cut that provider's share 25 to 30%. Wait a day. Grow more slowly than before. Do not answer a deferral with more volume.

If bounces mention a blocklist, stop raising volume and contact support. Once the address is delisted, restart the ramp lower.

What PostShiba does for you

A newly bought dedicated IP starts a 14-day warm-up when it first joins a cluster or a pool. Buying it in Network does not start the clock. Adding it does.

While it warms, the IP takes about 100 messages a day. With Use the cluster's IPs while warming up on (warmup_overflow), the rest goes out on the cluster's shared IPs, so your volume never waits. Turn overflow off only if every pooled message must leave from the pool's IPs and you can accept delays during the first two weeks.

After day 14 the IP sends at full rate. From then on, the share of mail you send with X-Capsule-Pool or X-Capsule-Ip decides how fast it grows.

PostShiba also slows delivery to a provider that defers, and keeps retrying. At Yahoo, if one tenant keeps hitting the limit, PostShiba pauses that tenant's Yahoo mail for an hour, and everyone else keeps sending.

Permanent bounces, spam reports, and unsubscribes go on the suppression list automatically. That keeps a known-bad address from counting against the new IP twice.

Keep IPs warm

An IP that stops sending loses its reputation over a few weeks. If a stream shrinks, take IPs out of the pool rather than spreading less mail over the same addresses.

When you add capacity to a warm pool, buy an IP and add it at a low weight. After day 14, raise the weight in steps: 10, then 25, then 50, then 100. Check the signals each time. Plan the pool first so you are not warming an IP you do not need.