Radio Relay International

Radio Relay International has developed a gateway for redirecting short Winlink messages to a cellular customer as a SMS (“text”) message without needing to know the recipient’s cellular service provider.

This service alleviates the need for users to use a service like to lookup the carrier’s gateway to send the message. This service was developed to provide short health and welfare messaging for the I AM SAFE program.

RRI SMS Gateway Flow Diagram

This service is one-way, restricted to licensed radio operators that send messages via the Winlink network. RRI is developing an additional service for MMS that will bypass the carrier’s email-to-MMS/SMS gateways and inject messages into the MMS network directly.


The following Winlink forms are available to support the gateway:


  • Download the RRI SMS GATEWAY FORM for the current form version maintained on this google
  • Unzip and copy both files either to:
    • Winlink’s Global template folder (if all Winlink users should have access)
      Typical path: C:\RMS Express\Global Folders\Templates
    • Winlink’s User Template folder (if only you should have access)
      Typical path: C:\RMS Express\CALLSIGN\Templates
      [whereas CALLSIGN = your callsign]
  • Run Winlink
  • Create a new message, and from the menu “Select template.”
  • Select the “RRI SMS.txt template from either the Global or User Template folder.
  • The form will open in a web browser for you to complete the message and cellular telephone to deliver to. When complete, submit and close the webrowser.
  • The form data will no be formatted and entered into a winlink message, ready to send. Do not modify any of its contents.
  • Send the message as you normally do
  • Text messages are usually received in minutes, however sometimes it may take a few hours to deliver. This is due to throttling the speed of emails relayed in order to prevent the appearance that the service is sending SPAM, which would result in service failures.


  • The current form version number is displayed at the bottom of the HTML form. This and the current service version is listed on this webpage at top.


Only messages originating from the are allowed to use the service. Users of this domain/service are FCC licensed radio operators.

Winlink allows users to transmit messages via a variety of modes, most notably via radio in areas that are completely cut off from commercial infrastructure (power, telephone, internet, cell service, satellite).

The Winlink Message is constructed using a form to ensure length doesn’t exceed carrier maximum length for SMS. The relevant data is send in three parts: The address (whereas X is the 10 digit US/CAN phone number); subject and body.

A receiving Winlink (RMS) server receives the message and forwards it onto a Winlink CMS server outside of the impacted area. The CMS server relays the winlink message as email to the Radio Relay International Gateway server.

The incoming message takes the phone number preceding the and uses an API to query a database for validity and to find who provides service for the number. It then returns that carrier’s email-to-SMS gateway (example, Verizon is and reassembles the two pieces as a new destination. The service then uses an additional API to relay the message using a transactional email server.

Logs are kept of all messages. There is no delivery confirmation from the carrier, and the service is one way.

The service has a high success rate but is reliant on the mobile phone carrier’s email to SMS service. As such, once the message has been delivered to the carrier, there is no delivery confirmation and it is reliant on the carrier to deliver. The service does not allow mobile phone users to return a message back. The service can, but does not send as a MMS message as in testing it was been discovered that some resellers (MVNOs) do not deliver reliably, despite working with SMS. Winlink forms are available to support the service and limit the length of message to ensure there is no truncation. Unlink MMS, SMS does not segment the message into parts.

Special Thanks to Marc at for use of their API for the Amateur Radio Community. The service boasts a %99 hit rate for US numbers. Thank you to N2NOV for resources of their VPS.

Please do not abuse this service as it is intended for health and welfare messaging.


  1. Will the service support MMS?
    We don’t want a service that only works some of the time, do we?  In developing this service it was discovered that some MVNO’s do not work with MMS, but do with SMS.   The inception for this project was to avoid needing to know a carrier to send a TXT, therefore providing a reliable and usable service. But yes, it can easily do MMS.
  2. Are there limitations?
    The service has not been stress tested, but exercises are planned to do so.
    -One carrier, US Cellular, has been been intermittent with delivery through their email-to-SMS gateway, however this is outside of the RRI service.
    -Length of message. RRI’s development of a direct MMS service aims to improve delivery and length.
  3. Can it be bi-directional?
    Yes it could, but it doesn’t.   This service is intended for health and welfare messaging.
  4. Can you track message receipt?
    No, only delivery to the carrier.
  5. What do I do if I have a failed message or problem?
    Send N1LJK a winlink message
  6. Can I help?
    The developer isn’t a programmer by trade.  He’s surprised he’s gotten this far.  So if you are, please, yes we need help!   Specifically we are looking for help with PHP and advanced mail server configuration.


Sending A SMS text message via the Winlink Radio Messaging Service

EXAMPLE: Offline with no other resources such as cell service or grid power, an emergency responder and Amateur Radio Operator sends a basic message to a concerned loved one outside of the impacted zone.  The only known information is the cell phone number. 

This is how it looks:

Winlink Software
Data entered into message
Photo of OH8STN Amateur Radio Winlink Station in field
Winlink transmitting message using VARA mode over HF Radio

It is transmitted over Radio to a Receiving Server.  These can be several miles, or thousands of miles away.

The Gateway parses the email to lookup the cell phone users provider and associated carrier.   It also looks up the carrier’s email-to-SMS gateway.

It then resends the email to the carrier’s service. 

The Carriers service ports the message as SMS into their network to the recipient.

Screenshot of received text message