Imported from ezekiell1988/bancos (.codex/skills/m1on1-send-email/SKILL.md). Install upstream with npx skills add ezekiell1988/bancos --skill m1on1-send-email. Copyright stays with the author.

m1on1-send-email

1. Paquete

MailKit 4.x (no usar System.Net.Mail.SmtpClient — está deprecado y falla con TLS moderno de SendGrid).

<!-- MarketingOneOnOneApi.csproj -->
<PackageReference Include="MailKit" Version="4.15.1" />

MimeKit se instala automáticamente como dependencia de MailKit.

2. Archivos clave

3. Contratos

SmtpEmailMessage (DTO)

// DTOs/SmtpDtos.cs
public record SmtpEmailMessage(
    string ToEmail,
    string ToName,
    string Subject,
    string HtmlBody
);

ISmtpEmailService

// Services/Interfaces/ISmtpEmailService.cs
public interface ISmtpEmailService
{
    Task SendAsync(SmtpEmailMessage message, ClientCustomerEmailSmtp config);
}

ClientCustomerEmailSmtp (Modelo BD — tabla tbClientCustomerEmailSMTP)

4. SmtpEmailService — implementación completa

using MailKit.Net.Smtp;
using MailKit.Security;
using MarketingOneOnOneApi.DTOs;
using MarketingOneOnOneApi.Models;
using MarketingOneOnOneApi.Services.Interfaces;
using MimeKit;
using MimeKit.Text;

namespace MarketingOneOnOneApi.Services;

public class SmtpEmailService : ISmtpEmailService
{
    private readonly ILogger<SmtpEmailService> _logger;

    public SmtpEmailService(ILogger<SmtpEmailService> logger)
    {
        _logger = logger;
    }

    public async Task SendAsync(SmtpEmailMessage message, ClientCustomerEmailSmtp config)
    {
        if (!int.TryParse(config.Port, out var port))
            throw new InvalidOperationException(
                $"Puerto SMTP invalido para customer {config.IdClientCustomer}: {config.Port}");

        var mimeMessage = new MimeMessage();
        mimeMessage.From.Add(new MailboxAddress(config.NameFrom, config.EmailFrom));
        mimeMessage.To.Add(new MailboxAddress(message.ToName, message.ToEmail));
        mimeMessage.Subject = message.Subject;
        mimeMessage.Body = new TextPart(TextFormat.Html) { Text = message.HtmlBody };

        // Puerto 465 = SSL implícito | 587 sslEnabled=true = STARTTLS | sin SSL = None
        var secureSocketOptions = port == 465
            ? SecureSocketOptions.SslOnConnect
            : config.SslEnabled
                ? SecureSocketOptions.StartTls
                : SecureSocketOptions.None;

        using var smtpClient = new SmtpClient();
        await smtpClient.ConnectAsync(config.Host, port, secureSocketOptions);
        await smtpClient.AuthenticateAsync(config.Username, config.Password);
        await smtpClient.SendAsync(mimeMessage);
        await smtpClient.DisconnectAsync(quit: true);

        _logger.LogInformation(
            "Email SMTP enviado a {ToEmail} para IdClientCustomer={IdClientCustomer}",
            message.ToEmail, config.IdClientCustomer);
    }
}

5. Registro DI

// Extensions/ApplicationServicesExtensions.cs
services.AddTransient<ISmtpEmailService, SmtpEmailService>();

AddTransient es correcto porque SmtpClient de MailKit es IDisposable y se crea/destruye por envío.

6. Cómo obtener la config SMTP desde BD

var smtpConfig = await _db.ClientCustomerEmailSmtps
    .AsNoTracking()
    .FirstOrDefaultAsync(c => c.IdClientCustomer == idClientCustomer);

if (smtpConfig == null)
{
    _logger.LogError("No existe config SMTP para IdClientCustomer={Id}", idClientCustomer);
    return;
}

7. Patrón de job Hangfire para envio de email

public interface IMyEmailJob
{
    [AutomaticRetry(Attempts = 0, OnAttemptsExceeded = AttemptsExceededAction.Fail)]
    Task SendAsync(int idLogin, int idClientCustomer /*, ...params */);
}

public class MyEmailJob : IMyEmailJob
{
    private readonly AppDbContext _db;
    private readonly ISmtpEmailService _smtpEmailService;

    public MyEmailJob(AppDbContext db, ISmtpEmailService smtpEmailService) { ... }

    [Queue("auth")]              // o la queue que corresponda
    [AutomaticRetry(Attempts = 0)]
    public async Task SendAsync(int idLogin, int idClientCustomer)
    {
        // 1. Cargar config SMTP
        var smtpConfig = await _db.ClientCustomerEmailSmtps
            .AsNoTracking()
            .FirstOrDefaultAsync(c => c.IdClientCustomer == idClientCustomer)
            ?? throw new InvalidOperationException("Sin config SMTP");

        // 2. Cargar datos del usuario
        var user = await _db.Logins.AsNoTracking()
            .FirstOrDefaultAsync(l => l.IdLogin == idLogin)
            ?? throw new InvalidOperationException($"IdLogin={idLogin} no existe");

        // 3. Leer template HTML
        var templatePath = Path.Combine(AppContext.BaseDirectory, "Templates", "Email", "mi-template.html");
        var html = await File.ReadAllTextAsync(templatePath);
        html = html.Replace("{{VARIABLE}}", WebUtility.HtmlEncode(valor), StringComparison.Ordinal);

        // 4. Construir mensaje y enviar
        var message = new SmtpEmailMessage(user.EmailLogin!, user.NameLogin, "Asunto", html);
        await _smtpEmailService.SendAsync(message, smtpConfig);
    }
}

Registrar el job en ApplicationServicesExtensions:

services.AddTransient<IMyEmailJob, MyEmailJob>();

8. Templates HTML

• Ubicación: src/MarketingOneOnOneApi/Templates/Email/
• Se copian al output con:

<!-- .csproj -->
<Content Include="Templates/**/*">
  <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
  <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
</Content>

• Variables en el template con {{NOMBRE_VARIABLE}} — reemplazadas con String.Replace(..., StringComparison.Ordinal).
• Siempre sanitizar con WebUtility.HtmlEncode() antes de inyectar valores en el HTML.

9. Lógica TLS — tabla de decisión

NUNCA usar System.Net.Mail.SmtpClient. Falla con TLS moderno (SendGrid, Gmail, etc.) con IOException: The connection was closed.

10. Anti-patrones

• ❌ new System.Net.Mail.SmtpClient(host, port) { EnableSsl = true } — no soporta TLS moderno.
• ❌ Hardcodear credenciales SMTP — siempre cargar desde tbClientCustomerEmailSMTP.
• ❌ No sanitizar con HtmlEncode al inyectar datos de usuario en el template.
• ❌ Registrar SmtpEmailService como Singleton — el SmtpClient de MailKit es IDisposable.