Add OverrideRecipientSMTP delivery method

[croaky]

Use the OverrideRecipientSMTP delivery method when you don't want your program
to accidentally send emails to addresses other than the overridden recipient
which you configure.

An example use case is in your web app's staging environment, your development
team will receive all staging emails without accidentally emailing users with
active email addresses in the database.

[dball]

If you're using ActionMailer, the mail_safe gem does this more flexibly:

https://github.com/myronmarston/mail_safe/

[croaky]

@dball Thanks for the link. I hadn't seen that one but have seen a number of similar solutions:

https://gist.github.com/138420
https://gist.github.com/2938882
http://blog.smartlogicsolutions.com/2009/04/25/reintroducing-sanitize_email-work-with-production-email-without-fear/
http://henrik.nyh.se/2012/08/abort-mail-delivery-with-rails-3-interceptors/
https://github.com/trampoline/actionmailer_extensions

It's definitely a common need!

It's common enough that I hope it will be accepted into the Mail gem, which I like as the home for this because:

• it's lower-level than ActionMailer
• I don't need to install a third-party gem that is more likely to get out of sync with the Mail gem or ActionMailer
• it's a simple implementation; most of the others involve some dirty monkey-patching

[killthekitten]

+1! I am the one of "the others involve some dirty monkey-patching"

[bcardarella]

-1 this doesn't seem like something that should go into the core gem but be extracted into a plugin.

If this is a Rails application you should have a specific config/environments/staging.rb and override the smtp settings so that the production mail server is not being used. I see the reason for the use case, but I would prefer to see the Mail gem modified to allow others to hook into it more easily.

[tinomen]

+1

[croaky]

Nudge @mikel. Your opinions on this pull request?

[mikel]

Hi there,

I like this, however, I think we should include the original values some how in the resulting email. ie, setting to, cc and bcc to nil is fine, however, perhaps we should store the original values as X-Override-To, X-Override-Cc and X-Override-Bcc.... that would make for better debugging for the developer as they could open the email and see who the email would have been sent to before it was overridden.

Make this change and appropriate tests and I think we can merge this in.

[croaky]

Sounds good, @mikel. I've pushed the requested change to 5f01a66. Let me know what you think.

[jeremy]

Better yet, leave the message's recipients intact! Check out #477 to set the SMTP envelope recipient directly: mail.smtp_envelope_to = '[email protected]'.

Side note: you can do this on your development machine using Postfix, too. In /etc/postfix/main.cf:

recipient_canonical_classes = envelope_recipient
recipient_canonical_maps = regexp:/etc/postfix/recipient_canonical_map

Create /etc/postfix/recipient_canonical_map containing /./ [email protected] and run postmap /etc/postfix/recipient_canonical_map and postfix reload.

That'll rewrite the recipient on every SMTP envelope to your catchall address.

[jeremy]

Also! This is a better fit for an interceptor than a delivery method:

class CanonicalEnvelopeRecipientInterceptor
  def initialize(recipient)
    @recipient = recipient
  end

  def delivering_email(mail)
    mail.smtp_envelope_to = @recipient
  end
end

Mail.register_interceptor CanonicalEnvelopeRecipientInterceptor.new('[email protected]')

[jeremy]

Closing in favor of using an interceptor to alter outgoing emails. That can be used with any delivery method, not just SMTP.