How to accomplish ringless voicemail using Asterisk

Hello experts,

I have a requirement where I need to send a voice mail message directly to someone’s mail box without ringing his phone. I know it is not an issue when implementing it for our own pbx accounts but the bottleneck is that I need to send Ring-less voicemail to PSTN and Cell phone users.

Any idea of moving forward in this direction? Awaiting your kind attention.


This isn’t something really Asterisk specific, it’s a question of if the provider for each can actually do that (ie: do you have a direct number to leave a voicemail). Asterisk can’t explicitly say “hey, don’t ring them just go to voicemail”.

Thanks for the response jcolp, Exactly same I am thinking that’s why I mentioned it in original post that its easy to do for asterisk setup but for PSTN and mobiles, I have no clue.
I was checking this site

and I think they are doing exactly same as you described that they need to contact with the voicemail servers of the PSTN or Cell phone providers. Can you shed some more light on the procedure and which tech to use for this when connection to provider’s voicemail system has been established?


That would be up to the provider.

hmmm… Thanks for your help… I will ask the client to talk with providers…but if providers allow then which dialplan functions we can use to send recorded messages to voicemail ?


There is no method of signalling this requirement across the PSTN, other than by dialling a different number, or, just possibly, although I’m not sure if DAHDI supports this, a different sub-address.

Basically, I think you have committed yourself to meeting an impossible requirement.

It also seems to me to be a questionable requirement, likely to be associated with phone spam.

Nice to see your response david… As I posted url above of stratics networks are implementing this service so I am interested in knowing what steps are required actually for me and what the client needs to do.

I haven’t undertaken the project yet by keen to take it :slight_smile:


I assume they have a special arrangement with all the networks to which they support such calls.

Actually, at least for mobile networks, voicemail is generally implemented by a call redirection to the server, but the server needs to know who did the redirection, and you need to be able to get that information past network border controls. You are only likely to be able to achieve the latter if you are both:

  • registered as a public network operator;

  • using ISDN (this sort of thing is unlikely to survive any SIP gateway).

Even then, I don’t know that Asterisk would be able to control that information. You may still have to connect to each network individually.

I’d suggest you need to hire specific expertise in the field or obtain and read documents that probably only a few hundred people have ever read.

Ok thanks alot… I will probably indulge myself in acquiring further knowledge about this as have seen lots of similar project on freelancing sites so it looks a nice research.

Thanks again for really detailed and spot on reply.


Stratics Networks Ringless Voicemail Drops has filed a few patents under there sister company.
Methods 1. Direct carrier cooperation meaning direct interconnects and dtmf codes provided by the carriers to access there VM cloud environment.
Method 2. Ringless Voicemail Drops Stratics Networks Carrier voicemail Block access codes (public codes for ppl) allowing anyone to access a vm direct however it looks like Stratics Networks has a bit of help on obtaining the codes by carriers as stated in the patent. Stratics Networks Ringless Voicemail Drops through there subsidiary, Ill link to the site here Stratics Networks Ringless Voicemail Drops

Honestly its not hard you just need the carrier contacts and about 20,000 vm acess codes.

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On a mildly hacked on asterisk server, I was able to set this up and drop voicemails in every number I tried (I owned or with permission) in about 40 minutes. I didn’t use any of the methods mentioned above. Just because you can do something, doesn’t mean you should. Yes, of course Asterisk can be used for nefarious purposes, however I, and I think you (whomever may be reading this) will find I and almost everyone here is going to be against giving advice on how to spam.

Hi all, Do you know someone that can create a Ringless Voicemail Drop system for my company ? Regards. Michael