outreach 'mailbox throttling limit exceeded' - agent's new mailbox capped at 20 sends a day

TL;DR

New Outreach mailboxes start with a low daily throttle (around 20 sends) and the agent blew past it. Respect the cap: queue the overflow for the next day, spread sends across warmed mailboxes, and ramp new mailboxes up gradually instead of full-blasting on day one.

outreach 'mailbox throttling limit exceeded'  -  agent's new mailbox capped at 20 sends a day

Steps

1. Read the throttle response and confirm the daily cap on the new mailbox. Expected: you know the exact per-day limit.

2. Stop the agent from retrying the throttled sends immediately. They will keep failing until the cap resets. Expected: the throttle errors stop.

3. Move the unsent messages into a next-day queue with their sequence position preserved, so nothing is skipped or duplicated when the cap resets. Expected: every message has a scheduled send slot.

4. Spread the load: route sends across older, warmed mailboxes that carry higher caps, keeping the new mailbox at or under its limit. Expected: total daily volume recovers without tripping any single mailbox.

5. Put new mailboxes on a warmup schedule in the agent: start low, raise the daily target gradually over a few weeks, and never assign a new mailbox more than its current cap. Expected: new mailboxes ramp without ever hitting the throttle.

Use this when

• 'mailbox throttling limit exceeded' appears on a recently added mailbox.
• A new sender was given a full sequence on its first day.
• Throttle errors cluster on one mailbox while others send fine.

Not for this skill when

• The mailbox is established and the throttle is account-wide (a different limit).
• Sends fail with authentication errors rather than throttle errors.
• Deliverability (bounces, spam complaints) is the problem, not volume caps.

Variant phrasings

• "outreach new mailbox send limit 20 per day"
• "mailbox throttling limit exceeded outreach agent"
• "outreach warmup throttle new sender"

Why it happens

Outreach throttles new mailboxes to protect sender reputation: a fresh mailbox that blasts hundreds of emails on day one looks exactly like a spam operation. The cap lifts as the mailbox builds a sending history. Agents that treat every mailbox as identical hit the new-mailbox wall on every fresh sender.

Edge cases

• The cap reset time is on Outreach's clock, not the agent's. Confirm the reset before resuming.
• Warmup schedules that ramp too fast re-trigger the throttle. Raise volume in small steps and watch for warnings.
• If a mailbox stays capped after weeks of clean sending, check for reputation flags on the domain, not just the mailbox.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_6nP15dEUfx96EBbOdNd67w