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# Sending Limits & Queue

Apple enforces pacing rules on every business that sends iMessage. They protect recipients from unwanted messages and protect your sender number from being throttled or blocked. Atlas Blue applies them automatically so your number stays in good standing.

The limits apply to outbound messages to contacts who have not replied, including contacts you upload. Replies to inbound messages are never limited.

## The Short Version

| Situation                                                                           | Limit                                              |
| ----------------------------------------------------------------------------------- | -------------------------------------------------- |
| **Replying to a contact who just messaged you**                                     | No limit                                           |
| **Messaging a contact who has replied before, but the conversation has gone quiet** | 2 minutes between messages to that contact         |
| **Messaging a contact who has never replied** (first message or follow-up)          | 15 minutes between each message, per sender number |
| **Unique contacts per 24 hours**                                                    | Recommended maximum of 1,000 per sender number     |
| **Sending window**                                                                  | 9:00 AM to 9:00 PM in your account's time zone     |

Limits apply to each sender number separately. Two numbers have twice the capacity.

## How the Limits Work

### 1. Replies to inbound messages are unlimited

When a contact messages you and you respond right away, there is no throttle. This is how iMessage is designed to be used, and Apple does not restrict it.

### 2. Re-engaging a contact who has replied before

If a contact has replied to you at some point but the conversation has been idle for several hours, Atlas Blue keeps a 2-minute gap between messages to that contact. This prevents Apple's systems from reading the message as part of a blast.

### 3. Initiating a conversation

When you message a contact who has never replied, Apple treats it as a new conversation initiation. A 15-minute gap is required between each initiation on a given sender number.

This is the rule that most affects outbound campaigns, because of two details:

* **Follow-ups count as initiations.** A second, third, or fourth message to someone who has not replied is treated exactly the same as the first. It takes a full 15-minute slot.
* **A reply changes everything.** As soon as a contact responds, they leave the 15-minute rule entirely and you can message them freely.

### 4. Daily contact recommendation

Apple recommends no more than 1,000 unique contacts per sender number in any 24-hour period. In practice the 15-minute initiation rule is a far tighter constraint for most outbound use cases, so this limit is rarely the one you hit.

## New Sender Numbers: Warm-Up Period

New sender numbers start with reduced limits and ramp up over the first week to establish a healthy reputation with Apple:

| Days since activation | Daily outbound limit |
| --------------------- | -------------------- |
| **Days 1-3**          | 10 messages          |
| **Days 4-8**          | 25 messages          |
| **Day 9 onward**      | 50 messages          |

Replies to inbound messages are not restricted during warm-up.

## Daily Capacity

Within a 9:00 AM to 9:00 PM sending window, the 15-minute initiation rule allows about 50 outbound messages per day, per sender number, to contacts who have not replied.

That 50 is a count of **messages, not new contacts**. Every unanswered follow-up uses one of those slots.

| Your sequence           | New contacts you can start per day (one number) |
| ----------------------- | ----------------------------------------------- |
| 1 message, no follow-up | \~50                                            |
| 2 touches               | \~25                                            |
| 3 touches               | \~17                                            |
| 5 touches               | \~10                                            |

Contacts who reply drop out of this math entirely, so higher response rates directly increase your outbound capacity.

There is no monthly quota. Limits are evaluated on a rolling 24-hour basis and per message interval.

## Sending Window

| Setting            | Value                                                                                                                                      |
| ------------------ | ------------------------------------------------------------------------------------------------------------------------------------------ |
| **Sending hours**  | 9:00 AM to 9:00 PM in your account's time zone. Nothing initiates outside these hours.                                                     |
| **Custom windows** | Set narrower windows inside the 9:00 AM to 9:00 PM range, including multiple windows in a single day. The range itself cannot be extended. |
| **Replies**        | Not restricted by the window                                                                                                               |

Messages that become eligible after 9:00 PM are held and sent starting at 9:00 AM the next day.

Sending windows are configured the same way as calling windows on voice campaigns — see [Call Scheduling](/docs/voice-ai/call-scheduling) — but voice campaigns dial 8:00 AM to 8:00 PM in the contact's local time, while Atlas Blue uses your account's time zone.

## Contact Status

Restrictions lift as a contact warms up:

| Status                                         | What applies                                                                                                                          |
| ---------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------- |
| **Never replied** (first message or follow-up) | 15-minute initiation spacing, the daily outbound limit, and the [first message rules](/docs/atlas-blue-campaigns/first-message-rules) |
| **Replied before, conversation idle**          | 2-minute gap between messages to that contact                                                                                         |
| **Active conversation**                        | No limits apply. Links, pricing, and follow-ups send right away.                                                                      |

Once someone replies, they stop consuming initiation slots. The limits are there to protect cold outreach, and a conversation that is already two-way is no longer cold.

## Message Queue

Atlas Blue does not reject messages that exceed the interval. They are placed in a queue and sent automatically as slots become available within the sending window.

Large batches take time to clear. Submitting 250 messages to new contacts in a single day takes roughly five days to deliver from one sender number. Spreading submissions across the week avoids this backlog.

A message blocked by the [first message rules](/docs/atlas-blue-campaigns/first-message-rules) is put back in the queue rather than dropped. Messages to contacts who already replied skip the queue entirely.

## Human-Like Reply Pacing

Messaging campaigns can pace agent replies so they arrive the way a person would
type them. Turn on **Human-Like Reply Pacing** in the campaign's schedule
settings, and Atlas will:

* Show the contact a **typing indicator** while the agent composes a reply.
* Delay each reply in proportion to its length, so **longer messages take a
  little longer to arrive**.
* Send **multi-part replies one bubble at a time** instead of all at once.

Conversations feel less automated as a result, which tends to improve engagement
and reply rates. A help icon next to the toggle explains the setting in the app.

## Why the Limits Matter: Report Junk

Apple monitors how recipients react to your messages. If even a small number of contacts — two or three — tap **Report Junk**, Apple may temporarily stop delivering messages from your number. This affects all of your sending, not just cold outreach. Repeated reports can result in the number being blocked on iMessage permanently.

The highest-risk message is an unanswered follow-up. Someone who has ignored three messages is far more likely to report the fourth than to respond to it.

## Best Practices

**Cap unanswered follow-ups at three.** After three messages with no reply, the contact is very unlikely to respond. Freeing those slots for new contacts improves results and reduces Report Junk risk.

**Spread large lists over multiple days.** Submit lists in daily batches sized to your available capacity rather than uploading everything at once.

**Respond to replies quickly.** Replies are unlimited, and a contact who has replied no longer consumes initiation slots. Fast responses both convert better and expand your capacity.

**Make the first message worth replying to.** A clear, relevant opening message that invites a response is the single most effective way to move contacts out of the 15-minute rule. See [First Message Rules](/docs/atlas-blue-campaigns/first-message-rules).

**Use opt-in where possible.** Contacts who message you first — for example via a "Text us" link or a form that opens iMessage — start the conversation on their side, so no initiation limit applies at all.

## Need More Capacity?

Because limits apply per sender number, adding a second number doubles your daily outbound capacity to roughly 100 initiations per day. Purchase additional numbers yourself from [Phone Number Setup](/docs/atlas-blue-campaigns/phone-number-setup) — each new number starts its own warm-up at 10 messages per day.