Building a high-quality sending reputation is key to ensuring email marketing effectiveness. To ISPs (such as Gmail and Yahoo), a new sending domain with no sending history is an unfamiliar source; sending in large volume from the start can easily be judged as spam and damage deliverability. That's why you need to gradually increase your sending volume through "warm-up" to build reputation step by step. MAAC has built warm-up into the system and handles it for you automatically—when you enable a new sending domain, or when a domain hasn't sent for over 30 days, the system automatically enters "Building Reputation" and gradually loosens the daily sending capacity, with no need to manually arrange a warm-up schedule. What this means for you: such domains start with a more conservative daily sending capacity, which then increases automatically based on sending performance.
This article explains how automatic warm-up works, the behavior you'll see during warm-up, and how to help build a stable domain reputation faster.
Understanding the basic operating mechanisms of email helps you understand why automatic warm-up is necessary.
The email ecosystem is dominated by Internet Service Providers (ISPs, such as Gmail, Yahoo, Microsoft Outlook). The primary task of these providers is to protect their users' inboxes from spam and malware.
Reputation System: ISPs score every IP address and domain that sends email. The higher the score, the easier it is for emails to enter the "Inbox"; if the score is too low, they will be thrown into the "Spam Folder" or rejected directly.
Risk Assessment of New Domains: For ISPs, any new sending domain without a historical sending record represents a potential risk. ISP systems default to imposing strict traffic limits and monitoring on unfamiliar sources.
Industry Standard: Warm-up is a universal standard procedure in global email marketing, not a limitation of a specific platform. As long as a new sending source is enabled, you must "introduce" yourself through progressive sending to gain the trust of ISPs. MAAC automates this process so you don't need to do anything manually.
How Email Automatic Warm-up Works
When your sending domain falls into one of the following situations, the system automatically sets it to the "Building Reputation" status and begins warm-up:
- A newly enabled sending domain: a domain used for sending for the first time.
- A sending domain inactive for a long time: a domain that hasn't sent any email for over 30 days and needs to rebuild reputation.
During warm-up:
- You can still create and send Broadcasts as usual.
- The system automatically controls and gradually loosens the daily sending capacity to build domain reputation steadily, with no manual adjustment needed. A new domain starts at about 350 emails per day, and then gradually loosens as you send consistently and your usage increases.
- If a broadcast's recipient count exceeds the day's safe sending volume, the excess contacts are automatically queued and continue sending later that day or the next day at 09:00 (in the time zone configured for your account).
- The broadcast status shows "Sending (Building Reputation)" to indicate the domain is warming up.
Once your domain has sent for a cumulative 14 days with a total sending volume of ≥ 50,000 emails, the system automatically upgrades it to "Healthy" status, marking the warm-up period as passed, and the daily sending capacity grows according to normal rules. The entire process requires no manual notification or action from you.
Automatic warm-up progress is tracked per sending domain; all Sender Profiles under the same sending domain share the same warm-up progress. For the full mechanics of domain health status, automatic throttling, and daily sending capacity, see: Feature Description | Email Sending Protection and Domain Health
How Daily Sending Capacity (Daily Capacity) Is Calculated
Each sending domain has a "today's sending limit" that the system calculates automatically. This number reflects the sending reputation accumulated between you and the platform—the more consistently you send, the higher your quota; long-term inactivity gradually reclaims it. (This limit only throttles Broadcasts; Customer Journeys are not subject to this limit and send as usual, but their sending volume still counts toward the domain's cumulative sends and usage—see "Multiple Broadcasts and Customer Journeys: How Sending Capacity Is Allocated" below.)
How daily sending capacity changes
Each day, the system adjusts the next day's capacity based on your average usage over the past 7 days:
| 7-day average usage | Next day's capacity change |
|---|---|
| Full (100%) | +50% (max increase) |
| About 70% | +20% |
| About 50% | No change |
| About 30% | −15% |
| No sending at all | −15% (max decrease) |
Design intent: a maximum daily increase of 50% (steady accumulation without spikes that hurt reputation) and a maximum decrease of 15% (occasional pauses won't reduce it significantly); because the system calculates based on the 7-day average, normal fluctuations such as weekend pauses or early-month promotions are not directly affected.
How many emails can you send per day during warm-up? (Growth trajectory)
A new domain starts at about 350 emails per day, after which the system recalculates dynamically each day based on your average usage over the past 7 days—there is no fixed daily schedule. The table below shows the ideal maximum growth curve when you use the full quota every day (100% usage), to help you understand the rate of growth:
| Warm-up day | Daily sending limit (approx.) |
|---|---|
| Day 0 (start) | 350 |
| Day 1 | ~525 |
| Day 3 | ~1,200 |
| Day 5 | ~2,700 |
| Day 7 | ~6,000 |
| Day 10 | ~20,000 |
| Day 14 | ~100,000 |
The table above is the ideal maximum growth curve when you use the full quota every day; in practice, usage is usually below 100%, so growth is slower than this. The key takeaway is the trend—more conservative early on, then loosening quickly as you send consistently—not the exact numbers. Once your domain has sent for a cumulative 14 days with a total volume of ≥ 50,000 emails, it automatically graduates to "Healthy" status; if it doesn't reach the threshold, it stays in "Building Reputation".
Does it keep growing after entering "Healthy"? Yes. In Healthy status, capacity continues to grow under the same rule (based on your 7-day average usage) and keeps climbing as long as usage holds up. If you're already near the limit and want even more sending capacity, reach out to your CSM / product consultant to request a higher sending cap.
What happens with long-term inactivity
- Decay floor (within 30 days of no sending): After about 9 days of no sending at all, the capacity drops to "half of what it was before you stopped" and holds there without dropping further; after you resume steady sending, it returns to its original limit in about 5–8 days. For example, if it was 100,000/day, two weeks of no sending lands it at about 50,000, and it can return to 100,000 within a week of resumed sending.
- Re-warm-up (30 consecutive days of no sending at all): The system determines that reputation needs rebuilding, switches the status back to "Building Reputation", and resets the capacity to about 350 emails per day, requiring another warm-up. This is because, after long-term inactivity, your sending reputation with Gmail, Yahoo, and others also gradually fades. How to avoid it: in the off-season, send at least a small batch of email once a month (such as a test email or internal notification) to keep the account active.
To get more sending capacity
- Send consistently: send every day; even small volumes still accumulate in the 7-day average.
- Keep usage above 50%: using more than half of the day's limit drives capacity growth.
- Avoid long pauses: more than a week triggers decay; more than 30 days triggers a reset.
- If you're already near your sending cap and want to go higher, reach out to your CSM / product consultant to request a higher sending cap; for time-sensitive, high-volume urgent sends, you can ask your CSM for a capacity increase (Healthy status only, up to 2× per increase).
Multiple Broadcasts and Customer Journeys: How Sending Capacity Is Allocated
If multiple broadcasts are scheduled at once, how is capacity allocated?
All Broadcasts under the same sending domain share the same daily sending capacity and are processed in order of scheduled time—the day's quota is not split evenly across multiple broadcasts.
・The system processes the earlier-scheduled A first: after A sends 5,000 emails, the day's quota is used up.
・B does not send that day (the quota is already used by A) and is automatically deferred to the next day.
・The two broadcasts do not each get 2,500.
Use two different sending channels (different sending domains/senders). Each sending domain has its own independent daily sending capacity, which is what allows true parallel high-volume sending.
Broadcasts vs. Customer Journeys: how sending volume is counted
Both send email, but their relationship with the "daily sending capacity" differs:
| Item | Broadcast | Customer Journey |
|---|---|---|
| Subject to the "daily sending capacity" limit | ✅ Yes (excess is automatically queued and continues the next day) | ❌ No (not throttled by this limit; sends as usual) |
| Counts toward the domain's cumulative sends and usage | ✅ Yes | ✅ Yes (counted the next day; affects capacity growth) |
| Its own sending limit | Based on the day's capacity | Can be set as the journey's Email message sending limit (no limit if unset) |
Although Customer Journeys are not subject to the daily sending capacity limit, their sending volume still affects how your domain reputation builds. During warm-up, we recommend keeping Customer Journey email sending steady as well and avoiding large one-time bursts, to protect your domain's long-term deliverability.
Example Scenario: How Is a 10,000-Contact List Sent?
Take a newly enabled account with a list of about 10,000 contacts as an example; different sending frequencies result in different experiences:
Scenario A: Sending all 10,000 at once
It will be throttled by the daily sending capacity and sent in batches, taking about 9–10 days to finish. After the first day sends the day's quota (such as about 350 emails), the system notifies you that "capacity is insufficient and sending will continue the next day"; the original broadcast stays in "Sending (Building Reputation)" status and automatically continues each subsequent day until everything is delivered. This is normal for a new domain, and contacts are not marked as failed because of it.
Scenario B: Sending once a week (common)
The cumulative volume over 14 days usually doesn't reach the 50,000-email graduation threshold, so the domain may stay in "Building Reputation" for a long time. But this does not affect your normal sending—for small to medium lists, "Building Reputation" and "Healthy" make almost no difference in sending speed or daily sending capacity.
Scenario C: Once a month or less
When the sending interval is too long, the low 7-day average usage causes the daily sending capacity to gradually decay (down to about half of its original value at most). If there is no sending at all for 30 consecutive days, the domain resets to "Building Reputation" and the daily sending capacity returns to about 350 emails per day. We recommend sending at least a small batch once a month during the off-season to stay active.
💡 List tips to improve warm-up results
Although warm-up is automatic, list quality still directly affects how fast your domain reputation builds. We recommend:
- Send to highly engaged audiences first: positive interactions such as opens and clicks help improve reputation.
- Avoid sending to unknown-source or long-inactive lists: an overly high bounce or spam complaint rate pushes the domain into "Warning/Restricted" status and triggers automatic throttling, or even "Suspended".
- Keep content compliant: avoid excessive exclamation marks, all-caps headlines, or an overly high ratio of images to reduce the risk of being marked as spam.
What Do You Need to Do?
Almost nothing extra. As long as you've completed Email channel activation, the system warms up automatically when you start sending. You only need to:
- Make sure Email channel activation and DNS verification are complete. 👉 See: Onboarding Guide | How to Enable Email Channels and Import Contacts
- Create and send Broadcasts as usual; a more conservative sending speed during warm-up is normal.
- Watch your list quality and content compliance to help the domain build a stable reputation faster.
During warm-up, you do not need to pause your Customer Journeys, and you don't need to create any dedicated warm-up journey or template.
FAQ
Q: Do I need to arrange a 14-day warm-up schedule myself?
No. MAAC automatically warms up new domains or domains that haven't sent for a long time, gradually increasing the daily sending capacity. You don't need to schedule anything manually or coordinate with the Crescendo Lab team.
Q: Will my broadcasts fail to send during warm-up?
No. You can still send normally during warm-up; anything beyond the day's safe sending volume is automatically queued and continues the next day at 09:00 (in the time zone configured for your account), and is not marked as failed.
Q: If the Sender Domain already has a reputation, is warm-up still needed when changing the sending source?
Yes. Sending reputation is bound to the combination of sending source and domain. Since the new sending source has no historical association with your domain, ISPs will view it as a suspicious source, and the system will automatically re-run warm-up to build ISP trust in this combination.
Q: If I don't send over the weekend, will my Monday capacity be cut?
It won't fluctuate noticeably. The system looks at your average usage over the past 7 days, so a 2-day weekend pause has little effect on the average; as long as you send on weekdays, your capacity won't drop noticeably.
Q: My list is only 50,000 but my capacity is 100,000—is that normal?
Yes. Daily sending capacity reflects "sending capability," not "list size." The system gives you roughly 2× your usual sending volume as buffer, so you can handle promotions or newly imported lists.
Q: I want to run a big promotion after a month of no sending—will I have enough capacity that day?
It depends on how long you paused. After 1–3 weeks of no sending, resuming about a week in advance gets you back to your original limit within 5–8 days; however, pausing for more than 30 days resets you to about 350 emails per day and requires another warm-up, so be sure to plan ahead.
Q: Is there a delay in calculating the capacity?
No. The system recalculates the day's capacity in the early morning each day, and it takes effect that same day.
Q: If I schedule two broadcasts at the same time, will they each get half the sending capacity?
No. All broadcasts under the same sending domain share the same daily sending capacity and are processed in order of scheduled time; the earlier-scheduled broadcast uses the quota first, and the later one is automatically deferred to the next day when the quota runs out. The capacity is not split evenly.
Q: How can I send two broadcasts in high volume at the same time?
Use two different sending channels (different sending domains/senders). Each sending domain has its own independent daily sending capacity, which is what allows true parallel high-volume sending.
Q: Once the day's sending capacity is used up, can Customer Journeys still send?
Yes. Customer Journeys are not throttled by the daily sending capacity limit and still send as usual. However, their sending volume counts toward the domain's cumulative sends and usage, which is included in the calculation the next day. During warm-up, we recommend avoiding large one-time bursts via journeys to protect your domain reputation.
Q: After entering "Healthy" status, does the daily sending capacity keep growing? How high can it go?
Yes. After entering Healthy status, capacity continues to grow under the same rule (based on your 7-day average usage) until it reaches your sending limit. If you need a higher limit, reach out to your CSM / product consultant to request a higher sending cap.
Q: Is there a limit on Customer Journey email sending?
You can set an Email message sending limit in the journey settings; if it's not set, there is no additional limit (it's still bound by your plan and account quotas).
📚 Further reading: