Email: receive, send, and queue

Poll a mailbox for inbound mail, send outbound mail over SMTP, and queue mail for background delivery.

What you'll build

A host using SquidStd.Mail.MailKit and SquidStd.Mail.Queue: an IMAP poller that raises a MailReceivedEvent for each new email, an SMTP sender (IMailSender), and a fire-and-forget send queue (IMailQueue) backed by messaging. The contracts live in SquidStd.Mail.Abstractions.

Prerequisites

.NET 10 SDK
dotnet add package SquidStd.Mail.MailKit
dotnet add package SquidStd.Mail.Queue
Real IMAP/SMTP credentials are only needed to actually connect; the sample compiles and runs without them.

Steps

1. Receive: poll a mailbox

AddMail registers an IMAP/POP3 poller; each received message is published as a MailReceivedEvent, which an IAsyncEventListener<MailReceivedEvent> handles.


bootstrap.ConfigureServices(container => container.AddMail(
        new MailOptions
        {
            Protocol = MailProtocolType.Imap,
            Host = "imap.example.com",
            Port = 993,
            Username = "alice@example.com",
            Password = "app-password"
        }
    )
);

2. Send: outbound SMTP

AddMailSender registers IMailSender; build an OutgoingMailMessage and call SendAsync.


bootstrap.ConfigureServices(container => container.AddMailSender(
        new SmtpOptions
        {
            Host = "smtp.example.com",
            Port = 587
        }
    )
);

3. Queue: background delivery

AddInMemoryMessaging plus AddMailQueue register IMailQueue; EnqueueAsync hands the message to a background consumer that sends it via the SMTP sender.


bootstrap.ConfigureServices(container => container
    .AddInMemoryMessaging()
    .AddMailQueue()
);

Run it

dotnet run --project samples/SquidStd.Samples.Email

It registers the poller, sender, and queue, registers the received-mail listener, and enqueues a message. Pass --send to also attempt a synchronous SMTP send (requires a reachable server).

How it works

The poller runs on the timer wheel, fetches new messages over IMAP/POP3 with MailKit, and publishes a MailReceivedEvent on the event bus. IMailSender maps OutgoingMailMessage to a MIME message and sends it. AddMailQueue layers a queue over SquidStd.Messaging: EnqueueAsync publishes to the queue and a background consumer (MailSendConsumerService) drains it through IMailSender, decoupling request latency from delivery.

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