# Voicemail detection and call-backs for voice agents

> Handle answering machines, missed calls and "call me tomorrow" in outbound voice agent calls: voicemail detection, campaign retries and automatic call-backs.

Source: https://vaakyo.com/blog/voicemail-detection-and-call-backs

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# When a machine answers: voicemail detection, retries and call-backs

A share of every outbound list reaches an answering machine or a busy customer. Detect voicemail, leave a short message, retry at the right time and book the call-backs people ask for.

The Vaakyo team 12 October 2026 3 min read

-   Outbound
-   Campaigns

On any outbound list, some calls don't reach a person ready to talk. A carrier's answering service picks up, the phone rings out, or the customer says "I'm driving, call me later". How your agent handles those calls decides how many customers you actually reach.

## Detect the machine

Turn on **voicemail detection** on the agent's **Call** tab. The call connects at once and the agent starts as usual, while the carrier listens for a few seconds and reports what answered:

-   **a person** : nothing changes;
-   **a machine** : the agent stops, speaks your **voicemail message** if you wrote one, and hangs up;
-   **unsure** : the call goes on as normal.

Keep the message short and useful on its own: who is calling, why, and how to reach you.

> Hi {name}, this is Asha from Acme Clinics about your appointment tomorrow. Please call us back on 080 4567 8900. Thank you.

The `{name}` is filled from each call's data, just like the welcome message. Every call records what answered it (`human`, `machine` or `unknown`), so you can see how much of a list is reaching machines.

## Retry the calls that didn't connect

In a campaign, choose which outcomes to call again: `no-answer`, `busy`, `failed` and, with voicemail detection on, `voicemail`. Then set how many retries and how long to wait between them.

A few rules that work well:

-   **One or two retries, not five.** Carriers and phone apps flag numbers that dial the same people again and again.
-   **A long gap.** Wait a few hours, so the next try lands at a different time of day. Someone who missed a 10 AM call may well answer at 6 PM.
-   **Stay inside calling hours.** Retries wait for the agent's calling hours, so nobody gets a call late at night.

When the retries run out, the contact's final outcome is in the campaign's results file, ready for your team to follow up another way.

## Book the call-back people ask for

"Call me tomorrow at 5" is a good outcome, not a failed call, as long as you actually call at 5.

Turn on **auto reschedule** . The agent can then book a call back during the conversation: it checks the time is in the future, within your limit (a week by default) and inside calling hours, confirms the day and time with the caller, and says goodbye. If the agent didn't book one, a short check of the transcript after the call catches requests it missed.

The call-back is an ordinary queued call: same agent, same number, same customer data. It waits until its time without holding a calling slot. In a campaign it counts as the contact's next attempt, and its outcome becomes the contact's outcome.

## What to measure

For each list, track the share of contacts reached by a person, reached by a machine, and never reached after retries. Also track how many call-backs were booked and how many of those connected. If machines take a large share, try a different time of day. If call-backs connect well, make sure your agent offers one whenever a customer sounds busy.

[Read next Interruptions, silence and goodbyes: tuning how a voice agent takes turns](https://vaakyo.com/blog/voice-agent-interruptions-and-silence)

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