Understanding Caller Health for Your Phone Numbers
What the Caller Health score on Account → Phone Numbers means, how the Healthy/Needs attention/Poor bands work, and what to do when a number needs attention.
General
Number Porting (Port-In)
Complete guide to porting your existing phone numbers to SIPSTACK, including timeline, requirements, and step-by-step process.
Port-Out Authorization
Complete guide to porting your phone numbers from SIPSTACK to another carrier, including PIN process, timeline, and service continuation.
Understanding Inconsistent Caller ID Names
Why the name displayed on a recipient's caller ID may differ from what you expect, and what can be done about it.
What is Carrier Transparency?
Carrier transparency refers to the mechanisms carriers use to identify callers and flag suspicious calls, including call labels, blocking notifications, and CNAM registration.
What is Call Spoofing?
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.
What is Short Stopping?
Short stopping is a telecom fraud scheme where a rogue carrier hijacks a legitimate call and reroutes it to an expensive premium-rate destination.
What is Call Stretching?
Call stretching is a telecom fraud method where fraudulent carriers inflate call duration to collect more termination revenue from legitimate carriers.
What is PBX Hacking?
PBX hacking is the unauthorized access to a business phone system, typically to place fraudulent international calls at the account owner's expense.
SIPSTACK Service Level Agreement (SLA)
Support tiers, severity levels, and response time targets for SIPSTACK customers.
What is Enhanced 911 (E-9-1-1)?
Enhanced 911 (E-9-1-1) is an emergency services system used in North America that provides a caller's location to dispatchers automatically.
What is Wangiri Fraud?
Wangiri is a one-ring phone scam designed to trick recipients into calling back a premium-rate number, incurring large charges.
What is CNAM?
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 (SMS/MMS)
Text messaging, or texting, is the act of composing and sending electronic messages, typically consisting of alphabetic and numeric characters, betwee...
Can SIPSTACK Numbers Receive SMS From a Short Code?
By default, SIPSTACK long code numbers cannot receive messages from short code numbers, but this can be enabled on request.
What is a Messaging Short Code?
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.
SIPSTACK Support for Opt-Out Keywords
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.
Does SIPSTACK Support Concatenated SMS Messages?
SIPSTACK supports sending and receiving concatenated SMS messages of up to 1,600 characters across Canada and US carriers.
Is MMS Supported for All Carriers in Canada and US?
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.
Will I Be Charged If SIPSTACK Encounters an Error When Sending an SMS?
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.
Sending and Receiving MMS Messages
How to send and receive MMS messages using SIPSTACK long code numbers in Canada and the US.
Carrier Support for PDF Files in MMS
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.
Does SIPSTACK Check If Phone Numbers Can Receive SMS?
SIPSTACK performs basic phone number validation before attempting delivery, but responsibility for providing accurate recipient numbers lies with the sender.
SMS Carrier Filtering in Canada and US
How wireless carrier filtering works, why messages get blocked, and what to do if your SIPSTACK SMS traffic is being filtered.
Capabilities of Long Code, Short Code, and Toll-Free Phone Numbers
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.
How to Use Toll-Free Phone Numbers for SMS and MMS
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.
API Rate Limits
How SIPSTACK API rate limiting works, including policies, HTTP response headers, and how to handle 429 errors.
Forbidden Message Categories for Toll-Free SMS and MMS
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.
Can I Send or Receive SMS With a SIPSTACK Toll-Free Number?
Yes, within Canada and the US, but only once the toll-free number is verified. Carriers block texts from unverified toll-free numbers.
Can my SMS messages arrive in order?
SIPSTACK cannot guarantee that SMS messages sent from your SIPSTACK phone number will arrive in order.
What Kind of Messages Are Restricted on SIPSTACK SMS?
SIPSTACK's Acceptable Use Policy prohibits spam, mass marketing, harassment, fraud, spoofing, and emergency service impersonation on the SMS platform.
What MMS Content Types Does SIPSTACK Support?
SIPSTACK MMS supports image, audio, video, text, and PDF file types up to 5 MB. Delivery depends on the recipient's carrier and device.
Why Are My MMS Messages Being Sent as SMS?
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.
Opt-Out Keyword Handling for Toll-Free SMS
Toll-free SMS numbers have carrier-level opt-out handling that operates independently of SIPSTACK. STOP and UNSTOP are handled at the network layer.
Can I Use SIPSTACK SMS for Emergency Purposes?
SIPSTACK SMS should not be used as a primary means of contacting emergency services. SMS communications to 911 are disabled by default.
A2P 10DLC Registration Campaign Types
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.
Handling Deactivated Phone Numbers
Best practices for identifying and removing deactivated phone numbers from your SMS contact lists to maintain deliverability and compliance.
Can My SMS Messages or Phone Numbers Be Blocked as Spam?
Yes. Wireless carriers can filter incoming SMS and MMS messages from numbers that show signs of spam or policy violations.
How Do I Register My Business for A2P 10DLC?
If you send business SMS to US recipients over 10-digit long code numbers, A2P 10DLC registration with The Campaign Registry (TCR) is required.
How Do Trust Scores for A2P 10DLC Affect Message Throughput?
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.
What is A2P and P2P Messaging?
A2P (Application-to-Person) and P2P (Person-to-Person) are the two categories of SMS traffic, each with different regulatory treatment and carrier handling.
What is A2P 10DLC?
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.