A new-contact slot is not a message count
The default allowance is 50 new contacts per sending number in a rolling 24-hour period. A number or organization can have a different configured limit. Replies and follow-ups do not use another new-contact slot, and adding a name to Contacts does not consume one.
Rolling 24 hours means capacity does not necessarily reset at midnight in the dashboard timezone. Earlier outreach ages out of the window as time passes. The Analytics date picker changes the report, not the sending allowance.
Pacing is a separate check
First messages to new people go out about eight minutes apart, varied a little each time, and never more than seven in an hour or two in ten minutes. Fifty new people take about seven hours rather than one: a number that reaches dozens of strangers an hour is what Apple stops trusting, and that is when its messages start going out as texts instead of iMessage. Follow-ups to people who have not replied keep the same pace, whether they go as iMessage, SMS or RCS; messages to anybody who has written back are not paced.
Having new-contact capacity does not mean every burst of messages will be accepted. Per-line pacing, duplicate detection, content checks, and availability still apply. Read the returned reason to tell these cases apart.
For API rate-limit responses, honor Retry-After when provided and use a bounded retry policy. Do not repeatedly press Send or run multiple workers against the same failed request hoping one will bypass the limit.
Every message counts toward 150 a day
Separately from new people, each number sends at most 150 messages in a rolling 24 hours, replies and follow-ups included. A number in ordinary two-way conversation stays well under it. An automated send past it — an automation, announcement, scheduled message or integration — waits and goes out by itself as the oldest messages of the day turn a day old; one that could not go within five days is refused with 429 daily_message_limit and a Retry-After.
What you type in the inbox is never held for the day: it goes now and still counts toward the 150. Through the API, mb or MCP, pass manual: true (mb send --manual) for one message a person asked to send now, never for bulk. Opt-outs, blocks and the 50 new people still apply.
Your project's Numbers page shows each number's messages against this total. Support can raise it for a number or your organization.
What Auto routing changes
Auto can choose among eligible project numbers for a new contact and save that choice. It keeps existing conversations on their saved number. A full or unavailable assigned line is not a reason to silently move an established customer conversation.
Plan expected outreach around the capacity you actually have. If your normal workload does not fit, ask support to review the setup and keep the customer’s expected sending identity consistent.
Do not assume a rejected request is queued
Check the operation’s actual response. A rejection is not a promise to send the message later. A pending message or queued integration job is different and should be inspected before retrying.
If an automation schedules later attempts, make it stop when a customer replies or opts out. Keep retries linked to the original workflow execution so they do not become new duplicate outreach.