What the Caller Health score on Account → Phone Numbers means, how the Healthy/Needs attention/Poor bands work, what a carrier spam flag (such as "Flagged as spam by T-Mobile") means, and what to do when a number needs attention.
Complete guide to porting your existing phone numbers to SIPSTACK, including timeline, requirements, and step-by-step process.
How to port a phone number from SIPSTACK to another carrier: unlock it on the Port-out tab in Switchboard, give the PIN to your new carrier, then cancel the account if you are leaving.
Why the name displayed on a recipient's caller ID may differ from what you expect, and what can be done about it.
Carrier transparency refers to the mechanisms carriers use to identify callers and flag suspicious calls, including call labels, blocking notifications, and CNAM registration.
Call spoofing is the illegal altering of Caller ID (CID) or Caller Name (CNAM) to deceive call recipients. Learn how it works and how to protect yourself.
Short stopping is a telecom fraud scheme where a rogue carrier hijacks a legitimate call and reroutes it to an expensive premium-rate destination.
Call stretching is a telecom fraud method where fraudulent carriers inflate call duration to collect more termination revenue from legitimate carriers.
PBX hacking is the unauthorized access to a business phone system, typically to place fraudulent international calls at the account owner's expense.
Support tiers, severity levels, and response time targets for SIPSTACK customers.
Enhanced 911 (E-9-1-1) is an emergency services system used in North America that provides a caller's location to dispatchers automatically.
Wangiri is a one-ring phone scam designed to trick recipients into calling back a premium-rate number, incurring large charges.
CNAM (Caller Name) is the caller name associated with an incoming phone call, displayed alongside the phone number on the recipient's device.
Text messaging, or texting, is the act of composing and sending electronic messages, typically consisting of alphabetic and numeric characters, betwee...
By default, SIPSTACK long code numbers cannot receive messages from short code numbers, but this can be enabled on request.
A short code is a 5 or 6-digit number used to send and receive high-volume SMS and MMS messages to and from mobile phones.
When a recipient replies with STOP, STOPALL, UNSUBSCRIBE, CANCEL, END, or QUIT to a SIPSTACK long code or toll-free number, they are automatically opted out.
SIPSTACK supports sending and receiving concatenated SMS messages of up to 1,600 characters across Canada and US carriers.
MMS support varies by carrier. SIPSTACK supports MMS to all major carriers in Canada and the US, and converts messages to SMS with a link for unsupported carriers.
SIPSTACK does not charge for messages that fail before delivery is attempted. Charges apply when delivery was attempted, regardless of whether the message reached the handset.
How to send and receive MMS messages using SIPSTACK long code numbers in Canada and the US.
PDF files are accepted by SIPSTACK MMS but are not supported by all carriers. Major Canadian carriers and AT&T do not support PDF attachments via long code MMS.
SIPSTACK performs basic phone number validation before attempting delivery, but responsibility for providing accurate recipient numbers lies with the sender.
How wireless carrier filtering works, why messages get blocked, and what to do if your SIPSTACK SMS traffic is being filtered.
A comparison of voice, SMS, MMS, throughput, and filtering characteristics for long code, toll-free, and short code phone numbers in Canada and the US.
Toll-free numbers can carry business A2P messaging in Canada and the US once they are verified and used within approved categories. Unverified toll-free numbers cannot send SMS.
How SIPSTACK API rate limiting works, including policies, HTTP response headers, and how to handle 429 errors.
Certain message categories are not permitted on toll-free SMS or MMS in Canada and the US. Messages in these categories will be rejected or may result in account suspension.
Yes, within Canada and the US, but only once the toll-free number is verified. Carriers block texts from unverified toll-free numbers.
SIPSTACK cannot guarantee that SMS messages sent from your SIPSTACK phone number will arrive in order.
SIPSTACK's Acceptable Use Policy prohibits spam, mass marketing, harassment, fraud, spoofing, and emergency service impersonation on the SMS platform.
SIPSTACK MMS supports image, audio, video, text, and PDF file types up to 5 MB. Delivery depends on the recipient's carrier and device.
When a recipient's carrier does not support MMS, SIPSTACK's MMS Converter automatically converts the message to an SMS with a URL linking to the media.
Toll-free SMS numbers have carrier-level opt-out handling that operates independently of SIPSTACK. STOP and UNSTOP are handled at the network layer.
SIPSTACK SMS should not be used as a primary means of contacting emergency services. SMS communications to 911 are disabled by default.
An overview of campaign types available for A2P 10DLC registration in the US, including standard declared use cases, mixed/marketing campaigns, and AT&T special use cases.
Best practices for identifying and removing deactivated phone numbers from your SMS contact lists to maintain deliverability and compliance.
Yes. Wireless carriers can filter incoming SMS and MMS messages from numbers that show signs of spam or policy violations.
If you send business SMS to US recipients over 10-digit long code numbers, A2P 10DLC registration with The Campaign Registry (TCR) is required.
Your A2P 10DLC Trust Score from The Campaign Registry determines how many message segments per second you can send over registered US long code numbers.
A2P (Application-to-Person) and P2P (Person-to-Person) are the two categories of SMS traffic, each with different regulatory treatment and carrier handling.
A2P 10DLC is the US carrier framework that requires businesses to register their brand and message campaigns before sending application-to-person SMS over 10-digit long code numbers.
