Automatic exclusion from the distribution of non-working email addresses

Imagine that you have a web application and one of its functions is the mass mailing of news to your users.
For some reason, part of the email addresses of users are non-working or incorrectly filled. Would such users be automatically unsubscribed?

You can add a special header to the email messages you send.

Return-Path: <noreply@my-application.com> 

Notifications from the mail server about failed deliveries will be sent to this address.
As a result, the whole task comes down to reading these notifications, retrieving the email address, and marking the user with this address as unavailable for distribution.

And now a real example.
In one of our applications, the mail server adds several useful lines directly to the body of such notifications:
')

 Final-Recipient: rfc822; nonexistent@example.com Original-Recipient: rfc822;nonexistent@example.com Action: failed Status: 5.1.1 

For ruby ​​there is an IMAP client in the standard library. Connect to our “noreply@my-application.com” mailbox and read the notifications:

 imap = Net::IMAP.new('mail.my-application.com', port: 993, ssl: true) imap.login("noreply@my-application.com", "mysecretpassword") imap.select("INBOX") #       ,    imap.search('ALL').each do |message_id| #    message = imap.fetch(message_id, 'BODY[TEXT]')[0].attr['BODY[TEXT]'] match = message.match(/^Original-Recipient: rfc822;(.*)$/) email = match[1].strip if match # rails-        if email user = User.where(email: email).first user.unsubscribe if user end #        imap.copy(message_id, 'Processed') imap.store(message_id, '+FLAGS', [:Deleted]) end imap.expunge imap.logout imap.disconnect 

For clarity, you can still check the status code. The code 5.XX indicates a fatal delivery error, for example, the email address does not exist, the code 4.XX indicates a temporary error, for example, the receiving server does not respond.
This code is run periodically in the background using Resque , Delayed :: Job , cron, or any other tool used in the application. Problem solved: mailing is sent only to working existing email addresses.

The task was prepared and solved together with olemskoi

PS: In your application, such notifications may not be so verbose, but you can still try to retrieve a non-working email. For example, if you use gmail to send emails, then notifications about a failed delivery from it will contain a specific header:

 X-Failed-Recipients: nonexistent@example.com 

which can be used.