Sequencer
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.
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. |
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?
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?
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?
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