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Deliverability is whether your email reaches the inbox. Braze publishes three IP warming schedules, a set of thresholds for bounces and spam reports, and tooling to suppress disengaged users. The work is mostly sequencing: what you configure before day one decides how much room you have later. The order matters more than any single setting.
Key Takeaways
- Delivery and deliverability are different things. A 99% delivery rate says nothing about which folder the mail landed in.
- A new IP has no history, so mailbox providers throttle it while they judge your first sends.
- Braze publishes three warming schedules. All three open at the same volume and differ in how fast the ramp compounds.
- Warming sends are real sends. Anything missing from the footer on day one is missing from every message in the ramp.
- The bounce and complaint figures are thresholds for investigating, not budgets to spend against.
- Most ISPs hold reputation data for 30 days, so a month of silence puts you back at the start.
What does deliverability actually mean here?
Braze draws a line between two words that get used interchangeably. Delivery is the share of emails accepted without a hard bounce. Deliverability is whether the message reaches the inbox instead of spam, and mailbox providers do not publish that as one number.
That gap is where reporting goes wrong. A delivery rate near 99% with bounces under 1% reads as healthy. It says nothing about which folder the mail landed in.
Why does a new IP address need warming?
A new IP has no history behind it. Mailbox providers throttle unknown senders to buy themselves time to judge. Braze gives a worked example: send to 100,000 users and a provider might deliver to only a fraction in the first hour.
What happens next depends on that fraction. Strong opens and clicks, and the throttle eases. Spam reports, and the rest of the send can be filtered.
Reputation is perishable too. Most ISPs keep reputation data for 30 days, so a month of silence puts you back at the start. Braze may also recycle IP addresses after three months of non-use, and a reassigned IP needs full warming regardless of what it did before.
Which warming schedule fits your situation?
Braze publishes three. All three open at the same volume and differ in how fast the ramp compounds.
| Day | Conservative | Moderate | Aggressive |
|---|---|---|---|
| 1 | 50 | 50 | 50 |
| 3 | 50 | 500 | 500 |
| 7 | 500 | 8,000 | 9,000 |
| 13 | 2,000 | 100,000 | 225,000 |
| 21 | 8,000 | 1,000,000 | Double daily |
| After | Double every 3 days | Double every 2 days | Double daily |
Conservative is the one to pick when you are new to email, moving off a shared IP, or recovering from throttling. Moderate is the documented default for most senders. Braze is explicit that aggressive suits senders with a proven record, and that using it without one can damage reputation.
Pick against your average daily volume, not your peak. Providers look at recent weeks, so warming to a seasonal high you hit twice a year leaves you maintaining a volume you cannot sustain.
What should be configured before day one?
Warming sends are real sends. Anything missing from the footer on day one is missing from every message in the ramp, and you cannot re-send them.
- Set the default sending domain in Email Preferences.
- Add a valid unsubscribe link to the custom footer.
- Turn on the list-unsubscribe header.
- Configure frequency capping for email.
- Split marketing, transactional and corporate mail across separate subdomains.
- Build the templates the ramp will use.
Step five is the one that gets deferred, and it is the expensive one to undo. Filtering now weighs domain reputation as well as IP reputation, so a single subdomain carrying receipts and promotions ties the two together permanently.
Which numbers tell you to slow down?
Braze publishes three thresholds worth watching during a ramp.
| Signal | Threshold | What it points at |
|---|---|---|
| Bounce rate | Above 3-5% on a campaign | List quality |
| Spam complaints | Above 0.08% on a campaign | Content and targeting |
| Unique open rate | Over 25% | Likely strong inbox placement |
Two of these are stop signals and one is a pass. That distinction gets lost when they are copied into a dashboard as a row of targets.
The bounce and complaint figures are thresholds for investigating, not budgets to spend against. A ramp sitting just under the complaint line is not passing. It is telling you the content is wrong for the audience you picked, and the ramp will compound that.
If bounces are the problem, the fix is upstream of Braze. If complaints are the problem, the fix is the send itself, and your work on dynamic content and personalisation is what moves it.
What goes wrong in the first month?
Four failure modes account for most of the damage, and three are avoidable by reading one page before you start.
1. Intelligent Timing during the ramp
Braze recommends against it for warming. The model has no engagement history to work from, so every message falls back to the same time, and you get none of the spreading you wanted.
2. Warming with the wrong content
Introductory sends need to be the most engaging mail you have. Your onboarding sequence is usually the best-performing thing in the workspace, which makes it the obvious ramp content. The activation campaigns already earning opens are the second place to look.
3. Stopping once the ramp finishes
Reaching target volume and then blasting weekly can undo the ramp. The cadence is the point, and it does not end on day 21.
4. Sending to everyone because volume is needed
The ramp creates pressure to fill a number, and the easiest fill is your least engaged users. Suppression lists exist for this: they hold users out by default even when a segment includes them, and exception tags let a final win-back through. That is the same list your retention work should already be feeding.
The claim that these four account for most first-month damage is a CustomerIK observation.
Frequently Asked Questions
1. Is mail landing in spam during warming a sign something is broken?
Not on its own. Braze documents this as normal early in a ramp, because the domain and IP have not built a reputation yet. Watch the trend across the ramp rather than any single day.
2. What happens if we pause sending for a month after warming?
You warm again. Most ISPs hold reputation data for 30 days, so a gap that long resets what the ramp built.
3. Can we use an IP that Braze previously assigned to someone else?
Braze may recycle addresses after three months of non-use, and recommends full warming for any newly assigned IP. Prior history is not something to plan around.
4. Should transactional mail go through the warming subdomain?
Braze recommends separating marketing, transactional and corporate mail across subdomains. Deciding that before the ramp costs nothing, and changing it afterwards means warming again.
5. Does a 99% delivery rate mean deliverability is fine?
It does not. Delivery counts what was accepted without a hard bounce. Inbox placement is a separate question, and opens are the closer proxy for it.
Sources
- Braze, IP warming. Retrieved 04 Sep 2026.
- Braze, Sunset policies for email. Retrieved 04 Sep 2026.
- Written by CustomerIK, a Braze implementation partner.
CustomerIK is a Braze implementation partner working across onboarding, technical integration, marketing operations and customer data management.
If you are warming an IP and the numbers are not moving the way you expected, let's talk.
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