rails: EOFError instead of SMTP error

FYI, there’s a whole bunch of non-net/smtp errors that leak out - here’s a list of exceptions that we’ve encountered on petition.parliament.uk:

  PERMANENT_FAILURES = [
    Net::SMTPFatalError,
    Net::SMTPSyntaxError
  ]

  TEMPORARY_FAILURES = [
    Net::SMTPAuthenticationError,
    Net::OpenTimeout,
    Net::SMTPServerBusy,
    Errno::ECONNRESET,
    Errno::ECONNREFUSED,
    Errno::ETIMEDOUT,
    Timeout::Error,
    EOFError
  ]

There’s a couple more to add to that list - OpenSSL::SSL::SSLError and SocketError. These occur when the DNS network is under a DDoS attack 😭

Even though Google is violating the RFC (“The receiver MUST NOT intentionally close the transmission channel until it receives and replies to a QUIT command (even if there was an error).”) by dropping the connection as soon as they send the 550, IMO net/smtp should probably ignore the protocol violation in favour of passing along the legitimate error it’s already received.

An EOFError in general (at some other, not-trying-to-quit-anyway, time) doesn’t strike me as entirely unreasonable to expose… but the missing backtrace seems improvable.

At that point, I don’t think we would need to do anything further: the Net::SMTPError in this case, and EOFError in the event of a more outright protocol violation, feels pretty consistent with how we handle exceptional circumstances elsewhere.

I opened a similar Ruby ticket to deal with the net/smtp letting the EOF out: https://bugs.ruby-lang.org/issues/13018

If that’s addressed on their end, I imagine the ActionMailer code would report it properly - if not, catching it and rethrowing the error with a stack trace would be a nice improvement in my view.

Looks like Google is dropping the connection unceremoniously. The SMTP client sends a QUIT and waits for a response which will never come.

EOFError is the expected exception for IO reads that expect a result but hit the end of the stream instead, and Net::SMTP#start documents that it may raise IOError (EOFError superclass).

Whether bubbling up the underlying net/protocol exceptions useful for developers is… a good question! Action Mailer uses Mail which uses Net::SMTP which uses Net::Protocol. Arguably, this EOFError could be rescued and raised as a protocol error from Net::SMTP then rescued and raised as a Mail delivery error rather than exposing the underlying transport error.

@sachin-metacube

I fixed the problem I was having. Maybe this will help you.

Step 1. Follow this guide here: https://support.google.com/a/answer/2956491 -> Be sure to enable TLS -> Make sure you’re using port 587 with TLS

Here are my Devise mailer settings:

  config.action_mailer.default_url_options = { host: 'localhost', port: 3000 }
  config.action_mailer.delivery_method = :smtp
  config.action_mailer.perform_deliveries = true
  config.action_mailer.raise_delivery_errors = true
  config.action_mailer.smtp_settings =
  {

    :address            => 'smtp-relay.gmail.com',
    :port               => 587,
    :domain             => 'gmail.com',
    :authentication     => :plain,
    :user_name          => ENV['MAILER_ADDRESS'],
    :password           => ENV['MAILER_SECRET'],
    :enable_starttls_auto => true
  }

I faced the same issue with Gmail SMTP. Adding

domain: 'mydomain.com' to the SMTP configuration fixed it for me.

One thing we may be able to do in Action Mailer is to improve the behaviour of the job class that handles deliver_later. Currently it’s pretty basic and all of the above errors leak out and generally in apps I write custom jobs to handle email delivery.