Sending email leads to an os error (invalid token)

[nkrofta]

Hi, I am trying to use lettre to send emails via the outlook smtp server smtp.office365.com:587. However, the send(...) function of AsyncSmtpTransport returns an error which I believe to be a bug.

The following code snippet shows the relevant part of my code:

pub struct MailTask {
    pub receiver: Mailbox,
    pub message: String
}

pub struct Mailman {
    mailbox_outlet: mpsc::Receiver<MailTask>,
    mail_account: Mailbox,
    transport: AsyncSmtpTransport<Tokio1Executor>,
    shutdown: ShutdownReceiver
}

impl Mailman {

    pub fn new(smtp_server: String, smtp_port: u16, mail_account: Mailbox, smtp_username: String, smtp_password: String, shutdown: ShutdownReceiver) -> (Mailman, mpsc::Sender<MailTask>) {
        let (mailbox, mailbox_outlet) = mpsc::channel(MAILBOX_SIZE);
        let credentials = Credentials::new(smtp_username, smtp_password);
        let transport: AsyncSmtpTransport<Tokio1Executor> = 
            AsyncSmtpTransport::<Tokio1Executor>::relay(&smtp_server)
            .unwrap()
            .port(smtp_port)
            .credentials(credentials)
            .build();
        let mailman = Mailman { mailbox_outlet, mail_account, transport, shutdown };
        (mailman, mailbox)
    }

    async fn deliver_mail(&self, task: MailTask) -> anyhow::Result<()> {
        let email = Message::builder()
            .from(self.mail_account.clone())
            .to(task.receiver)
            .subject("Email confirmation")
            .header(ContentType::TEXT_PLAIN)
            .body(task.message)
            .unwrap();
        self.transport.send(email).await.context("Failed to send mail")?;
        Ok(())
    }

}

The error (wrapped in an anyhow::Result with context "Failed to send mail"):

Failed to send mail

Caused by:
    0: Connection error: Connection error: Das Token, das der Funktion übergeben wurde, ist ungültig. (os error -2146893048)
    1: Connection error: Das Token, das der Funktion übergeben wurde, ist ungültig. (os error -2146893048)
    2: Das Token, das der Funktion übergeben wurde, ist ungültig. (os error -2146893048)

The German part means "The token given to the function is invalid." in English.
I am using Windows 11 and lettre v0.10.4.

[paolobarbolini]

Could you try using an SMTP server from a different provider in order to figure out whether it's a Microsoft issue or something else?

[nkrofta]

I've just tested it with Gmail, same outcome.

[paolobarbolini]

Are you by any chance putting in the port number together with the hostname parameter of relay?

[nkrofta]

You mean like "smtp.office365.com:587"? No, it's just "smtp.office365.com"

[rbaprado]

I am facing the same problem using AWS SES

Reference snippet:

    // Build the message
    let email = Message::builder()
        .from(from_mailbox)
        .to(to_mailbox)
        .subject(subject)
        .multipart(
            MultiPart::alternative() // This is composed of two parts.
                .singlepart(
                    SinglePart::builder()
                        .header(header::ContentType::TEXT_PLAIN)
                        .body(String::from(body_txt)), // Every message should have a plain text fallback.
                )
                .singlepart(
                    SinglePart::builder()
                        .header(header::ContentType::TEXT_HTML)
                        .body(String::from(body_html)),
                ),
        )
        .unwrap();

    // Setup credentials
    let creds = Credentials::new(SETTINGS.smtp_user.clone(), SETTINGS.smtp_password.clone());

    // Open SMTP connection
    let mailer = AsyncSmtpTransport::<Tokio1Executor>::relay(&SETTINGS.smtp_host)
        .unwrap()
        .credentials(creds)
        .port(SETTINGS.smtp_port)
        .build();

    // Send the email
    let send_result = mailer.send(email).await;

[rbaprado]

Solved (at least for my case): changed relay() to starttls_relay()