Email with Attachments (.NET)¶

Use ACS Email when you need to send reports, invoices, or diagnostic bundles from an app or worker.

Attachment limits

Keep each attachment under 10 MB and send no more than 10 attachments per email.

Setup¶

using Azure.Communication.Email;

var client = new EmailClient(Environment.GetEnvironmentVariable("ACS_EMAIL_CONNECTION_STRING"));

Create attachments from file bytes¶

using Azure;
using Azure.Communication.Email;

var pdfBytes = await File.ReadAllBytesAsync("invoice.pdf");
var pngBytes = await File.ReadAllBytesAsync("chart.png");

var attachments = new List<EmailAttachment>
{
    new EmailAttachment("invoice.pdf", "application/pdf", BinaryData.FromBytes(pdfBytes)),
    new EmailAttachment("chart.png", "image/png", BinaryData.FromBytes(pngBytes)),
    new EmailAttachment("summary.csv", "text/csv", BinaryData.FromBytes(await File.ReadAllBytesAsync("summary.csv")))
};

Send the message¶

var message = new EmailMessage(
    senderAddress: "DoNotReply@contoso.com",
    recipientAddresses: new[] { "user@contoso.com" },
    content: new EmailContent("Monthly package")
    {
        PlainText = "Attached are the invoice and supporting files.",
        Html = "<p>Attached are the invoice and supporting files.</p>"
    });

message.Attachments.AddRange(attachments);

var response = await client.SendAsync(WaitUntil.Completed, message);
Console.WriteLine($"Message id: {response.Value.MessageId}");

Base64 and BinaryData¶

When a workflow needs a base64 string first, convert the raw bytes yourself and still pass BinaryData to ACS.

var base64 = Convert.ToBase64String(pdfBytes);
Console.WriteLine(base64[..24] + "...");

Multiple attachment types¶

Type	Example
`application/pdf`	Invoice
`image/png`	Screenshot
`text/csv`	Export
`application/zip`	Archive

Practical guidance¶

Prefer links for large payloads

If the payload approaches the size limit, upload it to Blob Storage and include a SAS link instead.

Full example¶

using Azure;
using Azure.Communication.Email;

var client = new EmailClient(Environment.GetEnvironmentVariable("ACS_EMAIL_CONNECTION_STRING"));

var attachments = new List<EmailAttachment>
{
    new("invoice.pdf", "application/pdf", BinaryData.FromBytes(await File.ReadAllBytesAsync("invoice.pdf"))),
    new("summary.csv", "text/csv", BinaryData.FromBytes(await File.ReadAllBytesAsync("summary.csv")))
};

var message = new EmailMessage("DoNotReply@contoso.com", new[] { "user@contoso.com" },
    new EmailContent("Invoice attached")
    {
        PlainText = "Invoice and summary are attached.",
        Html = "<p>Invoice and summary are attached.</p>"
    });

message.Attachments.AddRange(attachments);

await client.SendAsync(WaitUntil.Completed, message);

Sources¶

https://learn.microsoft.com/azure/communication-services/quickstarts/email/send-email-advanced/send-email-with-attachments
https://learn.microsoft.com/azure/communication-services/concepts/email/email-attachment