Ringless Voicemail API - Best Practices

Ringless Voicemail is a unique tool to use to message your customers without interrupting their daily lives, giving you the ability to deliver voicemails to a customer’s mobile voicemail box without a call. Today, the majority of mobile devices transcribe these messages for users so even if they don’t listen, they will likely read your message.

This tool can also be cost-effective without the need to employ live operators for conducting outbound calls. Send appointment reminders, event updates, or even links to tickets using RVM.

Some things you need to know:

Your Ytel account is rate limited. What does this mean? On a per account level, you can send a maximum of 150 API calls per second. This is not per API function, this is across the board for the account. Keep this in mind when using Ytel API for multiple functions. I.g. SMS, Calls, and RVM.

RVM success is dependent on delivery and response rates. We will touch on best practices for delivery below however it is important to note if response rates are not at the expected level, it likely is the messaging itself.

Best practices for highest delivery

Lookup Carrier

Many customers do not know that RVM is a strategy that works only on mobile numbers. This misunderstanding can lead to a skewed perception of delivery rates and can cause frustration. Ytel has a solution for this! Our Lookup Carrier API can provide you with the information you are looking for. If a number is not mobile, no need to send an RVM. If a number is mobile, send away.

Audio Length

Ytel’s RVM has a minimum and maximum requirement for audio files being dropped on your customer’s voicemail. All audios must be between 30-60 seconds.

Audio quality

It is important to note, voice to text (transcription of the audio) at the voicemail box level is done by the handsets and not by Ytel. Even with the best technology in voice-to-text transcription on handsets, we highly suggest using professional voice services for your audio. For example, if you are trying to leave a clickable URL or clickable number on the voicemail transcription, it is likely the link will not be properly transcribed if the audio is poor. Furthermore, Ytel always suggests running your own quality assurance on your recordings to make sure the message is delivering as you expect.


As RVMs are being delivered, it is important to note that a “blip” on the phone could occur and the caller id that is displayed on the handset is the RVMCallerID.

We recommend the use of NumberSets when sending out RVM, this will allow us to manage the CallerIDs used.

Forward Numbers

Ytel always suggests that you forward all of your numbers to IVR to filter interested callers. This increases the efficiency of live agents receiving callbacks. You want to keep your agents available taking calls from interested parties and not just any callback. You can do this by applying Inbound XML to your API numbers.

Number Management

Number management is a large part of RVM deliverability. Every RVM requires two numbers, a From number and a RVMCallerID. For best deliverability cycle through your numbers when making these RVM calls, changing the From and RVMCallerID numbers on your calls. Keep in mind, there is a rate limit on API calls of 150 per second that you should be mindful of. Below is the suggested amount of numbers to use based on the Contacts Per Hour (CPH) you are messaging to.

We recommend the use of NumberSets when sending out RVM, this will allow us to manage the CallerIDs used. Please make sure your NumberSet used has adequate numbers in it per the below requirements.

Max RVM Per Day

Phone Number pairs

Total Phone Number






















Did this page help you?