# Campaign sending limits and mailbox rotation

> How many emails a campaign actually sends. The campaign daily limit, each mailbox's own cap, pacing gaps, and how campaigns share mailboxes.

Source: https://emailpal.io/help/campaign-sending-limits-and-mailbox-rotation

## The limits that apply

An email goes out only when every limit allows it. The lowest one wins.

| Limit | Where you set it | Range or default |
| --- | --- | --- |
| Campaign **Daily limit** | Campaign **Settings**, **Daily limit and priority** | 1 to 10,000. New campaigns start at 30. |
| **Max new leads per day** | Same card | Optional. Caps how many new people start each day. |
| Mailbox daily cap | The mailbox's cold-email limit | Never above 100. [Sending limits per mailbox](/help/sending-limits-per-mailbox). |

The **Daily limit** hint shows how much your selected mailboxes can send together. The campaign sends at most that many, whatever you type.

## The mailbox cap is a rolling 24 hours

A mailbox cap is not "per calendar day". It is the number of sends in the last 24 hours. When a mailbox hits its cap, the next send waits until the oldest one in the window is 24 hours old.

Everything sent from the mailbox counts toward that cap: every campaign's emails and the replies you send from Unibox. Warming traffic does not. [Do warmup emails count toward sending limits?](/help/do-warmup-emails-count-toward-sending-limits)

## Pacing between emails

In **Advanced options**, under **Stopping and pacing**:

- **Minimum gap between emails** is the wait between sends from the same mailbox. The default is 9 minutes.
- **Random extra gap** adds a random amount up to this many minutes on top, so sends do not look mechanical. The default is 5 minutes.

Each mailbox can also set its own **Minimum wait between sends** in its mailbox settings, next to its **Reply-to address** and **Tracking domain**.

## Which mailbox sends to which lead

When a lead enters a campaign it is tied to one mailbox, and its follow-ups come from that same mailbox. The mailbox is the one with the lightest projected load for its size, which keeps one mailbox from hoarding follow-ups while another sits idle.

- **Match sender to recipient provider** (under **Deliverability**) prefers Google mailboxes for Gmail addresses, Microsoft mailboxes for Outlook, and so on.
- If a mailbox is removed from the campaign or deleted, its leads move to the least-loaded mailbox that is left.
- Any mailbox that is not on hold or unavailable can be picked, including one that is still warming. [When is a mailbox ready to send?](/help/when-is-a-mailbox-ready-to-send)

## When campaigns share a mailbox

Several campaigns can use the same mailbox. They share its cap by priority:

| Priority | Weight |
| --- | --- |
| High | 2 |
| Normal | 1 |
| Low | 0.5 |

A higher priority gets a bigger share of the mailbox's sends. A campaign with nothing to send does not hold its share back for others.

**Start new leads before follow-ups** changes the order when a mailbox is close to its cap. It prefers starting new people over sending follow-ups.

A follow-up that falls more than the stale limit overdue (7 days by default, set by **Flag leads with no follow-up after** in the Engage workspace settings) is not sent late. The lead is marked **Expired** instead.

## FAQs

### Can I raise a mailbox above 100 a day?

No. 100 is a ceiling shared with the mail server. Add more mailboxes and spread them across more domains. [How many mailboxes per domain?](/help/how-many-mailboxes-per-domain)

### Why is my campaign sending fewer than its daily limit?

The mailbox caps and schedule windows sit below the daily limit. The lowest wins. **Diagnose** shows what is holding a campaign back.

### Do my Unibox replies use up the cap?

Yes. They count in the same rolling 24 hours as campaign emails.

### Does the daily limit reset at midnight?

The campaign's daily count follows the first schedule's time zone. The mailbox cap does not reset at midnight, because it is a rolling 24 hours. [Schedules and time zones](/help/campaign-schedules-and-time-zones)

## Need More Help?

[Create a campaign](/help/create-a-campaign), [Auto-pause on bounces](/help/campaign-auto-pause-and-circuit-breakers).