Messaging Rate Limits

SMS (10DLC)

SMS rate limits are determined by your 10DLC campaign type and vetting score. These limits are set by carriers, not by AgentPhone, and apply to all A2P (application-to-person) messaging in the US.

If you exceed your rate limit, messages are not dropped. AgentPhone automatically enqueues them and delivers each message as soon as throughput becomes available.

Daily message limits

T-Mobile publishes per-day segment caps based on campaign type and trust score. Since T-Mobile typically represents about one-third of US mobile traffic, you can estimate your total daily capacity by tripling the T-Mobile figure.

Campaign type	T-Mobile daily limit	Estimated total daily limit
Sole proprietor	1,000 segments	~3,000 segments
Low volume	2,000 segments	~6,000 segments
High volume -low trust	2,000 segments	~6,000 segments
High volume -standard	10,000 segments	~30,000 segments
High volume -high trust	40,000 segments	~120,000 segments
High volume -highest trust	200,000 segments	~600,000 segments

A segment is a 160-character chunk of a standard SMS (or 70 characters for Unicode). A single message may count as multiple segments if it exceeds these limits.

High volume vetting scores

High volume campaigns go through a third-party vetting process that assigns a trust score. Your score determines which throughput tier you land in. Companies without an established reputation may initially receive the same 2,000 segment T-Mobile cap as low volume campaigns, even on a high volume campaign. The limit increases as your trust score improves.

Throughput (messages per second)

In addition to daily caps, carriers enforce per-second throughput limits:

Campaign type	Throughput
Sole proprietor	2.25 MPS
Low volume	3.75 MPS
High volume -standard	12 MPS
High volume -high trust	120 MPS
High volume -highest trust	225 MPS

Exceeding your limits

When your sending rate or daily volume exceeds carrier limits, AgentPhone queues the excess messages and sends them as capacity frees up. You do not need to implement retry logic on your end. Messages will be delivered in order as throughput becomes available.

For time-sensitive campaigns, plan your send volume against the limits above to ensure messages arrive within your expected window.

Increasing your limits

Your limits are tied to your 10DLC campaign registration and vetting score. To improve your throughput:

Register a high volume campaign if you’re currently on low volume or sole proprietor.
Schedule a call with us and we’ll help you through the registration and vetting process.

iMessage

iMessage limits are based on whether a contact messaged you first and how recently they interacted with your number.

Scenario	Counts against	Limit
A contact texts you (inbound)	Inbound limit	1,000 contacts/day/line
You reply within 24 hours of their last message	No limit	Unlimited messages
You message first after 24 hours since their last message	Follow-up limit	200 contacts/day/line

How it works

Inbound conversations: When a contact messages your number, that counts toward the 1,000 contacts/day/line inbound cap. Once a conversation is open, you can send unlimited replies as long as you respond within 24 hours of their most recent message.
Follow-ups: If more than 24 hours have passed since a contact’s last message and you initiate a new message, that counts toward the 200 contacts/day/line follow-up cap.
Limits are per-line: Each phone number has its own independent limits.

If you need higher inbound or follow-up capacity, we recommend load balancing across multiple numbers on your end. Each additional line gives you another full set of daily limits.