Delivery Receipts (DLRs)

DLRs apply to all message sending methods — the Phonovation SMS API v2, the legacy v1 APIs, and messages sent directly through the Phonovation web interface. If a message is sent, a DLR can be generated.

When a message is delivered (or fails), the Phonovation gateway sends an HTTP POST to a URL you provide. This lets you track delivery status in real time for every message you send.

Setup

Provide your DLR callback URL to support@phonovation.com. The endpoint must:

Accept HTTP POST requests
Return a 200 OK response

DLR parameters

The POST body contains the following fields:

Parameter	Example	Description
`SMS-Type`	`Notification`	Always `Notification`
`SMS-NotifyId`	`321354`	The `notifyId` you assigned to the recipient
`SMS-Success`	`True`	`True` if delivered, `False` if not
`SMS-To`	`353871111111`	Destination number (GSM format)
`SMS-From`	`353877777777`	Sender ID as it appeared on the recipient’s handset
`SMS-Verify`	`9db038748b3088971d913616c13e769b`	MD5 hash for payload verification — see below
`SMS-TotalToSend`	`1`	Total number of messages in the send
`SMS-TotalSent`	`1`	Number successfully sent
`SMS-TotalFailed`	`0`	Number that failed
`SMS-TimeStamp`	`2024-01-10 14:17:44`	Delivery time (`yyyy-MM-dd HH:mm:ss`, UTC)

Success logic

SMS-Success is True only when all messages were delivered:

DLR success rule

TotalSent == TotalToSend AND TotalFailed == 0  →  True
Otherwise  →  False

TotalToSend	TotalSent	TotalFailed	SMS-Success
2	2	0	`True`
2	1	1	`False`

DLR timing

The vast majority of DLRs — 90%+ — arrive within seconds to a few minutes of sending. However, DLRs are ultimately dependent on the downstream mobile network and the recipient’s device. In some cases a DLR may be delayed by up to 48 hours due to:

Network congestion or outages
High traffic volumes
The recipient’s device being powered off or out of coverage

Design your integration to handle late DLRs. Do not assume a message has failed simply because a DLR has not arrived quickly. If you require a hard timeout, 48 hours is a safe threshold after which you can treat a missing DLR as unconfirmed.

Example DLR payload

SMS-Type=Notification
SMS-NotifyId=
SMS-Success=True
SMS-To=353861234567
SMS-From=353871234568
SMS-Verify=5fb4926bd7e461eddc6dc629f472bab4
SMS-TotalToSend=1
SMS-TotalSent=1
SMS-TotalFailed=0
SMS-TimeStamp=2026-04-09 16:03:16

URL-encode the POST body before sending. Some field values may contain characters that break unencoded requests.

Verifying the payload

The SMS-Verify field is an MD5 hash you can use to confirm the DLR genuinely came from Phonovation:

Verification formula

MD5(SMS-NotifyId + SMS-Success + YourClientSecret)

curl -X POST https://example.com/sms/dlr \
  -H "Content-Type: application/x-www-form-urlencoded" \
  -d "SMS-NotifyId=order-001&SMS-Success=True&SMS-Verify=EXPECTED_MD5_HASH"

const crypto = require('crypto');

function verifyDlr({ notifyId, success, clientSecret, verify }) {
  const expected = crypto
    .createHash('md5')
    .update(notifyId + success + clientSecret)
    .digest('hex');
  return expected === verify;
}

import hashlib

def verify_dlr(notify_id, success, client_secret, verify):
    expected = hashlib.md5(
        f"{notify_id}{success}{client_secret}".encode()
    ).hexdigest()
    return expected == verify

using System.Security.Cryptography;
using System.Text;

bool VerifyDlr(string notifyId, string success, string clientSecret, string verify)
{
    var input = Encoding.UTF8.GetBytes(notifyId + success + clientSecret);
    var hash = MD5.HashData(input);
    var expected = Convert.ToHexString(hash).ToLowerInvariant();
    return expected == verify;
}

import java.security.MessageDigest;
import java.util.HexFormat;

boolean verifyDlr(String notifyId, String success, String clientSecret, String verify) throws Exception {
    MessageDigest md5 = MessageDigest.getInstance("MD5");
    byte[] hash = md5.digest((notifyId + success + clientSecret).getBytes());
    String expected = HexFormat.of().formatHex(hash);
    return expected.equals(verify);
}

function verifyDlr($notifyId, $success, $clientSecret, $verify) {
    $expected = md5($notifyId . $success . $clientSecret);
    return $expected === $verify;
}

Tracking recipients with notifyId

Set a notifyId per recipient when sending and Phonovation will echo it back in every DLR for that recipient via SMS-NotifyId. The same identifier also appears in webhooks, making it the single thread that ties your outbound send, webhook confirmation, DLR, and inbound replies together. See notifyId for full details, use cases, and end-to-end flow examples.

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Setup

DLR parameters

Success logic

DLR timing

Example DLR payload

Verifying the payload

Tracking recipients with notifyId

​Setup

​DLR parameters

​Success logic

​DLR timing

​Example DLR payload

​Verifying the payload

​Tracking recipients with notifyId

Setup

DLR parameters

Success logic

DLR timing

Example DLR payload

Verifying the payload

Tracking recipients with notifyId