Send email from a .Net Framework Winforms application and service using Microsoft accounts.

Question

Hello.

We provide a .Net Framework Winforms application with a service. Both share code which allows our customers to send email from their own email accounts, currently using MailKit, although we could use another client if necessary.

Where they want to use Microsoft accounts, will they be able to continue to use their username and password? If they choose to use OAuth instead, how would we implement this so that the Winforms application can be configured once, sends mail, and the service can also pick up those credentials? Is that possible? I've tried to follow both Microsoft and MailKit's documentation on MSAL, but it's not clear to me which approach to implement.

Many thanks

Jon

Answer 1

Hi @Fortecho Solutions Ltd , Welcome to Microsoft Q&A,

To send emails from a Microsoft account from a WinForms application or service, you can choose to use OAuth2 for authentication. OAuth2 is more secure than traditional usernames and passwords.

In the service, read the stored token and use it to authenticate and send emails:

public class EmailService
{
    private static readonly string tokenCachePath = "token_cache.json";

    public async Task SendEmailAsync(string to, string subject, string body)
    {
        var token = File.ReadAllText(tokenCachePath);

        var message = new MimeMessage();
        message.From.Add(new MailboxAddress("Your Name", "your-email@example.com"));
        message.To.Add(new MailboxAddress("", to));
        message.Subject = subject;
        message.Body = new TextPart("plain")
        {
            Text = body
        };

        using var client = new SmtpClient();
        await client.ConnectAsync("smtp.office365.com", 587, MailKit.Security.SecureSocketOptions.StartTls);
        await client.AuthenticateAsync("your-email@example.com", token);
        await client.SendAsync(message);
        await client.DisconnectAsync(true);
    }
}

Best Regards,

Jiale

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