Does the service work on landline phones?

It sends to US and Canadian mobile numbers and select landlines. To be compatible, a landline must have voicemail provided by its phone service provider. The service does not connect to PBX systems, and when sending to those phone systems users may experience a short ring.

Do delivery credits expire?

Monthly plan credits expire 30 days after purchase and do not roll over. Pay As You Go credits do not expire. Either way, the sender is charged only for successfully delivered voicemails.

What does Voicemail Personalization do?

It sends personalized voicemails using the sender's own voice or text-to-speech, inserting the recipient's first name into the message. The feature costs two credits per successful delivery and is enabled by contacting support.

Can several people share one account?

Yes. Corporate accounts let an admin account create subaccounts, allocate delivery credits to them, and view each subaccount's campaign history.

Direct mail & outbound

Slybroadcast

Slybroadcast is a ringless voicemail service. A pre-recorded message is delivered into a recipient's voicemail box without ringing the phone, and the recipient sees a voicemail from whatever caller ID the sender supplies.

A campaign is set up by recording a message by phone or uploading an audio file, uploading a contact list as a comma-delimited or tab-delimited file, setting the caller ID, and sending immediately, in batches, or on a schedule. Delivery reports show results in real time, and a purchased callback number adds callback reporting and forwards return calls to any number. Campaigns can also be sent and monitored from the mobile app.

Add-ons include follow-up texting, which sends an automated text right after a voicemail is delivered and requires a purchased callback number, and Voicemail Personalization, which uses text-to-speech or a cloned voice to insert a recipient's first name. Each costs two credits per successful delivery. Integrations cover Zapier, Make, Salesforce, and Integrately, API access is included with every account, and corporate accounts allow subaccounts with allocated credits.

Delivery reaches United States and Canadian mobile numbers and select landlines that have voicemail from their phone provider; the service does not connect to PBX systems, where callers may hear a short ring. Senders pay only for delivered messages. Monthly plan credits expire 30 days after purchase and do not roll over, while pay-as-you-go credits do not expire. The site is operated by MobileSphere LLC.

Best for

Operators running owner or tenant outreach who want pre-recorded messages left in voicemail without ringing the phone. Delivery covers US and Canadian numbers only and does not reach PBX phone systems.

What they do

Ringless voicemail drops
Scheduled and batch voicemail campaigns
Follow-up text messaging
Callback numbers with call forwarding
Callback reporting and delivery analytics
AI voice personalization
Mobile app campaign sending
Contact list management
API access
Corporate accounts with subaccounts

Details

Attribute	Value
How they charge	Pay only for delivered drops: 100 for $12, 250 for $24, 500 for $45, 1,000 for $70, 5,000 for $250. Callback numbers are $15 per month per line.

What stands out

Says over 3 million people send voicemails using its patented ringless technology
Delivers to US and Canadian mobile numbers and select landlines, but does not connect to PBX systems
Senders are charged only for successfully delivered voicemails
Callback numbers cost $15 per month per line and unlock callback reporting
Integrates with Zapier, Make, Salesforce, and Integrately, with API access included in every account

Common questions

Does the service work on landline phones?: It sends to US and Canadian mobile numbers and select landlines. To be compatible, a landline must have voicemail provided by its phone service provider. The service does not connect to PBX systems, and when sending to those phone systems users may experience a short ring.
Do delivery credits expire?: Monthly plan credits expire 30 days after purchase and do not roll over. Pay As You Go credits do not expire. Either way, the sender is charged only for successfully delivered voicemails.
What does Voicemail Personalization do?: It sends personalized voicemails using the sender's own voice or text-to-speech, inserting the recipient's first name into the message. The feature costs two credits per successful delivery and is enabled by contacting support.
Can several people share one account?: Yes. Corporate accounts let an admin account create subaccounts, allocate delivery credits to them, and view each subaccount's campaign history.