Email API Documentation | PHP & C# Examples

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ℹ️

Verified sending domain required: the accountName parameter must be a verified email address registered in your iSMS account. Complete the Domain Setup steps before your first API call.

🚀 Overview

One POST endpoint sends plain-text or HTML emails, with or without a file attachment.

What You Can Send

🔑 OTP & Verification

Send one-time passwords and email verification codes securely.

🧾 Invoices & Receipts

Transactional emails triggered automatically by your billing system.

📢 Marketing Campaigns

Bulk promotional emails to opted-in customer lists.

🔔 System Alerts

Automated alerts for system events, error logs, or threshold triggers.

📰 Newsletters

Regular subscriber newsletters with HTML content and images.

📎 With Attachments

Send PDFs, reports, and documents as email attachments.

🔗 API Endpoint

Send an HTTP POST request with form fields. One endpoint is used for all email sends.

POSThttps://smtpapi.vocotext.com/isms_send_email_smtp_api.php

Setting	Value
Method	POST
Content-Type	multipart/form-data
Attachments	Supported

ℹ️

Use multipart/form-data encoding for all requests, especially when sending attachments. Standard application/x-www-form-urlencoded is sufficient for text-only emails.

🔧 Domain Setup Requirements

Before sending emails via the API, your sending domain must be verified and properly configured. These records authenticate your sender domain. Delivery and inbox placement also depend on your content, sending practices and recipient mail systems.

Prepare Your Domain

Ensure you have a dedicated domain for sending emails — e.g. yourcompany.com or mail.yourcompany.com. A dedicated domain improves sender reputation.

Verify Domain Ownership

Add a verification TXT record to your domain's DNS settings. Contact iSMS support for your specific verification token.

Configure DNS Records

Set up SPF, DKIM, DMARC, MX, and CNAME records as provided by iSMS to authenticate your sending domain.

Create Sender Email

Configure the verified sender email address and display name (fromAlias) in your iSMS account. Use this as the accountName parameter.

⚠️

The accountName parameter must be a verified email address registered in your iSMS account. Unverified addresses will be rejected. Contact us to set up your sending domain.

🧩 Request Parameters

All parameters are submitted as multipart/form-data POST fields. The attachment field is optional.

Parameter	Type	Required	Description
un	String	Required	Your iSMS account username
pwd	String	Required	Your iSMS account password
toEmail	String	Required	Recipient's email address — e.g. `recipient@domain.com`
subject	String	Required	Email subject line
body	String	Required	Email body content — supports plain text or HTML
accountName	String	Required	Verified sender email address (registered in your iSMS account) — e.g. `noreply@yourcompany.com`
fromAlias	String	Required	Display name shown to the recipient — e.g. `My Company Notifications`
agreedterm	String	Required	Must be set to `YES` to confirm acceptance of iSMS Terms & Conditions
attachment	File	Optional	File attachment — submitted as a multipart file upload. Supports PDF, images, documents, etc.

🐘 PHP Example — Text/HTML Email

Basic email sending without attachment. Use http_build_query() for simple form-encoded POST when no file attachment is needed.

PHPsend_email.php

<?php
$url = 'https://smtpapi.vocotext.com/isms_send_email_smtp_api.php';

$postData = [
    'un'          => 'your_username',
    'pwd'         => 'your_password',
    'toEmail'     => 'recipient@domain.com',
    'subject'     => 'Your Invoice #INV-2024-001',
    'body'        => '<h2>Thank you for your order</h2>
                     <p>Your invoice is ready. Please find the details below.</p>',
    'accountName' => 'noreply@yourcompany.com',  // Must be verified
    'fromAlias'   => 'My Company Billing',
    'agreedterm'  => 'YES'
];

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($postData));

$response = curl_exec($ch);

if (curl_errno($ch)) {
    echo 'cURL error: ' . curl_error($ch);
} else {
    echo 'Response: ' . $response;
}

curl_close($ch);
?>

📎 PHP Example — With File Attachment

When sending a file attachment, use CURLFile to properly encode the file in a multipart request. Do not use http_build_query() — pass the array directly to CURLOPT_POSTFIELDS.

Attachment Notes

✦ Use CURLFile (PHP 5.5+) for file uploads — avoid deprecated @filepath syntax
✦ Do not use http_build_query() when sending attachments — it does not handle file uploads
✦ mime_content_type() auto-detects the MIME type of the file
✦ Maximum attachment size depends on your server's PHP post_max_size and upload_max_filesize settings

PHPsend_email_with_attachment.php

<?php
$url = 'https://smtpapi.vocotext.com/isms_send_email_smtp_api.php';

// File attachment — can be a path from $_FILES or a server-side path
$attachmentPath = '/path/to/invoice.pdf';
$attachmentName = 'invoice_2024.pdf';

$postData = [
    'un'          => 'your_username',
    'pwd'         => 'your_password',
    'toEmail'     => 'client@domain.com',
    'subject'     => 'Your Invoice is Attached',
    'body'        => '<p>Please find your invoice attached.</p>
                     <p>Thank you for your business!</p>',
    'accountName' => 'noreply@yourcompany.com',
    'fromAlias'   => 'My Company Billing',
    'agreedterm'  => 'YES'
];

// Attach file using CURLFile (PHP 5.5+)
if (file_exists($attachmentPath)) {
    $postData['attachment'] = new CURLFile(
        $attachmentPath,
        mime_content_type($attachmentPath),  // Auto-detect MIME
        $attachmentName
    );
}

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

// Pass array directly — NOT http_build_query() — so CURLFile works
curl_setopt($ch, CURLOPT_POSTFIELDS, $postData);

$response = curl_exec($ch);

if (curl_errno($ch)) {
    echo 'cURL error: ' . curl_error($ch);
} else {
    echo 'Response from API: ' . $response;
}

curl_close($ch);
?>

Handling File Upload from Web Form

PHPsend_email_form_upload.php

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {

    // Get file details from uploaded form $_FILES
    $attachmentPath = $_FILES['attachment']['tmp_name'] ?? null;
    $attachmentName = $_FILES['attachment']['name'] ?? null;

    $url = 'https://smtpapi.vocotext.com/isms_send_email_smtp_api.php';

    $postData = [
        'un'          => $_POST['un'],
        'pwd'         => $_POST['pwd'],
        'toEmail'     => $_POST['toEmail'],
        'subject'     => $_POST['subject'],
        'body'        => $_POST['body'],
        'accountName' => $_POST['accountName'],
        'fromAlias'   => $_POST['fromAlias'],
        'agreedterm'  => 'YES'
    ];

    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    if ($attachmentPath && $attachmentName) {
        $postData['attachment'] = new CURLFile(
            $attachmentPath,
            mime_content_type($attachmentPath),
            $attachmentName
        );
        curl_setopt($ch, CURLOPT_POSTFIELDS, $postData);  // Array — NOT encoded
    } else {
        curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($postData));
    }

    $response = curl_exec($ch);
    curl_close($ch);

    echo 'Response: ' . $response;
}
?>

🔷 C# Example — Windows Forms / .NET

Full C# implementation using HttpClient and MultipartFormDataContent. Compatible with .NET Framework and .NET Core.

C#EmailSender.cs

using System;
using System.IO;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;

public class EmailSender
{
    private static readonly string apiUrl =
        "https://smtpapi.vocotext.com/isms_send_email_smtp_api.php";

    public static async Task<string> SendEmailAsync(
        string username, string password,
        string toEmail, string subject, string body,
        string accountName, string fromAlias,
        string attachmentPath = null)
    {
        using var client   = new HttpClient();
        using var formData = new MultipartFormDataContent();

        // Required fields
        formData.Add(new StringContent(username),    "un");
        formData.Add(new StringContent(password),    "pwd");
        formData.Add(new StringContent(toEmail),     "toEmail");
        formData.Add(new StringContent(subject),     "subject");
        formData.Add(new StringContent(body),        "body");
        formData.Add(new StringContent(accountName), "accountName");
        formData.Add(new StringContent(fromAlias),   "fromAlias");
        formData.Add(new StringContent("YES"),       "agreedterm");

        // Optional attachment
        if (!string.IsNullOrEmpty(attachmentPath) &&
            File.Exists(attachmentPath))
        {
            var fileContent = new ByteArrayContent(
                File.ReadAllBytes(attachmentPath));
            fileContent.Headers.ContentType =
                MediaTypeHeaderValue.Parse("multipart/form-data");
            formData.Add(fileContent, "attachment",
                Path.GetFileName(attachmentPath));
        }

        var response = await client.PostAsync(apiUrl, formData);
        return await response.Content.ReadAsStringAsync();
    }
}

// Usage:
// var result = await EmailSender.SendEmailAsync(
//     "your_username", "your_password",
//     "client@domain.com", "Your Invoice",
//     "<p>Please find attached.</p>",
//     "noreply@yourcompany.com", "My Company",
//     @"C:\invoices\inv001.pdf"  // optional
// );

Need Email API Access or Domain Setup Help?

Our team will help you verify your sending domain, configure DNS records, and test your first email delivery.

Contact Developer Support → View Email Service Overview