SendGrid Email Connector

Transactional and bulk email via the SendGrid v3 API.

Package

dotnet add package Ratatosk.Sendgrid

Required settings

Parameter	Type	Description
ApiKey	string	SendGrid API key (starts with SG.)

Optional settings

Parameter	Type	Default	Description
SandboxMode	bool	false	When true, no email is actually sent (for testing)
WebhookUrl	string	—	URL for event webhooks
TrackingSettings	string	—	JSON with click/open tracking settings

Schema

Property	Value
Provider	SendGrid
Type	Email
Version	1.1.0
Capabilities	SendMessages, BulkMessaging, Templates, HealthCheck
Content types	PlainText, Html, Multipart, Template
Endpoints	EmailAddress (send + receive)
Authentication	API Key

Send examples

Plain text email

var settings = new ConnectionSettings()
    .SetParameter("ApiKey", "SG...");

var connector = new SendGridEmailConnector(SendGridChannelSchemas.SendGridEmail, settings);
await connector.InitializeAsync(ct);

var email = new MessageBuilder()
    .WithId("email-1")
    .FromEmail("noreply@yourdomain.com")
    .ToEmail("user@example.com")
    .WithText("Welcome to the app!")
    .WithSubject("Welcome!")
    .Build();

var result = await connector.SendMessageAsync(email, ct);

HTML email

new MessageBuilder()
    .FromEmail("noreply@yourdomain.com")
    .ToEmail("user@example.com")
    .WithHtml("<h1>Welcome!</h1><p>Thanks for signing up, <b>{{name}}</b>.</p>")
    .WithSubject("Welcome!")
    .Build();

Multipart email (text + HTML)

var multipart = new MultipartContent();
multipart.Parts.Add(new TextContent("Welcome to the app! Please verify your email."));
multipart.Parts.Add(new HtmlContent(
    "<h1>Welcome!</h1><p>Please <a href='{{link}}'>verify your email</a>.</p>"));

new MessageBuilder()
    .FromEmail("noreply@yourdomain.com")
    .ToEmail("user@example.com")
    .WithContent(multipart)
    .WithSubject("Verify your email")
    .Build();

Email with attachment

new MessageBuilder()
    .FromEmail("noreply@yourdomain.com")
    .ToEmail("user@example.com")
    .WithHtml("<p>Please find the attached report.</p>", html =>
    {
        html.Attachments.Add(new MessageAttachment(
            "report", "report.pdf", "application/pdf", base64PdfContent));
    })
    .WithSubject("Monthly Report")
    .Build();

Template email (SendGrid dynamic templates)

new MessageBuilder()
    .FromEmail("noreply@yourdomain.com")
    .ToEmail("user@example.com")
    .WithContent(new TemplateContent("d-abc123def456", new Dictionary<string, object?>
    {
        ["name"] = "Alice",
        ["verification_link"] = "https://example.com/verify?token=xyz"
    }))
    .WithSubject("Welcome!")
    .Build();

Batch send

var batch = new MessageBatch();
batch.Messages.Add(email1);
batch.Messages.Add(email2);
batch.Messages.Add(email3);

var result = await connector.SendBatchAsync(batch, ct);
Console.WriteLine($"Batch sent: {result.Data?.BatchId}");

if (result.Data != null)
{
    foreach (var (msgId, sendResult) in result.Data.MessageResults)
        Console.WriteLine($"  {msgId}: {sendResult.Status} ({sendResult.RemoteMessageId})");
}

Sandbox mode (testing)

new ConnectionSettings()
    .SetParameter("ApiKey", "SG...")
    .SetParameter("SandboxMode", true);

Message properties

Property	Type	Description
Subject	string	Email subject line (required)
TrackingSettings	string	JSON string for click/open tracking configuration
ReplyTo	string	Reply-to email address

Webhook handling

SendGrid posts event data (delivered, opened, clicked, bounced, spam reports) as JSON POST to your webhook URL:

[HttpPost("/webhooks/sendgrid")]
public async Task<IActionResult> SendGridWebhook(CancellationToken ct)
{
    using var reader = new StreamReader(Request.Body);
    var body = await reader.ReadToEndAsync(ct);
    var source = MessageSource.Json(body);

    var result = await _connector.ReceiveMessageStatusAsync(source, ct);
    // Process status updates...

    return Ok();
}

Validate X-Twilio-Email-Event-Webhook-Signature header when using signed webhooks.

Error codes

SendGrid-specific error codes are defined in SendGridErrorCodes with domain "SendGrid".

Code	Description
INVALID_EMAIL_ADDRESS	Email address format is invalid
MISSING_EMAIL_CONTENT	Email content (subject, body) is missing

Standard MessagingErrorCodes are also used — see the error codes reference.

Original provider codes

SendGrid errors are mapped from HTTP status codes in the connector. There is no custom error code mapping from SendGrid API error codes. HTTP 429 Too Many Requests maps to RATE_LIMIT_EXCEEDED; all other non-success status codes map to SEND_MESSAGE_FAILED.

Troubleshooting

Symptom	Likely cause	Fix
INVALID_CREDENTIALS	API key is invalid	Generate a new API key in SendGrid UI
PROVIDER_VALIDATION_FAILED	Invalid sender email	Verify sender domain (SPF/DKIM setup)
Delivery not happening	Sender not verified	Verify sender email or domain in SendGrid
Emails going to spam	Poor sender reputation	Check SendGrid reputation reports
Template not rendering	Template ID wrong	Verify template ID in SendGrid UI
Event webhooks not arriving	Webhook URL not configured	Subscribe to events in SendGrid Mail Settings

SendGridChannelSchemas

// Full email schema (send, bulk, templates)
SendGridChannelSchemas.SendGridEmail