{"id":442,"date":"2026-09-26T01:30:59","date_gmt":"2026-09-26T07:00:59","guid":{"rendered":"https:\/\/photonconsole.com\/blog\/?p=442"},"modified":"2026-09-26T08:00:02","modified_gmt":"2026-09-26T13:30:02","slug":"ruby-on-rails-actionmailer-smtp-configuration-and-delivery-reliability","status":"publish","type":"post","link":"https:\/\/photonconsole.com\/blog\/ruby-on-rails-actionmailer-smtp-configuration-and-delivery-reliability\/","title":{"rendered":"Ruby on Rails ActionMailer: SMTP Configuration and Delivery Reliability"},"content":{"rendered":"\n

ActionMailer is one of the most pleasant parts of Rails. Generate a mailer, write a view, call deliver_later<\/code>, and email works. Locally, at least.<\/p>\n\n\n\n

In production the same code can fail without a sound. No exception, no log entry, no failed job. The controller returns a success response, the user waits for a password reset that never arrives, and nothing in your monitoring suggests anything happened.<\/p>\n\n\n\n

That silence is a configuration default, not a bug. This guide covers the production setup: SMTP settings that actually connect, the flag that hides every delivery error, queuing with ActiveJob, mailer previews, and the errors Rails developers hit most often.<\/p>\n\n\n\n

Quick Answer: How Do You Configure ActionMailer SMTP?<\/h2>\n\n\n\n

Set the delivery method and SMTP settings in your production environment file:<\/p>\n\n\n\n

# config\/environments\/production.rb\nconfig.action_mailer.delivery_method = :smtp\nconfig.action_mailer.perform_deliveries = true\nconfig.action_mailer.raise_delivery_errors = true\nconfig.action_mailer.default_url_options = { host: \"yourapp.com\", protocol: \"https\" }\n\nconfig.action_mailer.smtp_settings = {\n  address:              \"smtp.photonrelay.com\",\n  port:                 587,\n  domain:               \"yourdomain.com\",\n  user_name:            ENV[\"SMTP_USER\"],\n  password:             ENV[\"SMTP_PASS\"],\n  authentication:       :plain,\n  enable_starttls_auto: true,\n  open_timeout:         5,\n  read_timeout:         5\n}<\/code><\/pre>\n\n\n\n
class UserMailer < ApplicationMailer\n  default from: \"noreply@yourdomain.com\"\n\n  def welcome(user)\n    @user = user\n    mail(to: @user.email, subject: \"Welcome to Your App\")\n  end\nend\n\nUserMailer.welcome(user).deliver_later<\/code><\/pre>\n\n\n\n
Three lines in that configuration matter more than the rest, and the next sections explain why. Delivery itself depends on the server you authenticate against and whether your domain is authorised to send \u2014 an authenticated relay such as PhotonConsole<\/a> covers that side.<\/p>\n\n\n\n
How ActionMailer Delivers<\/h2>\n\n\n\n
ActionMailer builds the message and hands it to a delivery method. The Rails guides<\/a> document four, and only one sends real mail over the network.<\/p>\n\n\n\n
Delivery method<\/th>What it does<\/th>Use in<\/th><\/tr><\/thead>
:smtp<\/code><\/td>Sends over SMTP to the configured server<\/td>Production<\/td><\/tr>
:sendmail<\/code><\/td>Pipes to a local sendmail binary<\/td>Rarely \u2014 usually unauthenticated<\/td><\/tr>
:file<\/code><\/td>Writes each message to tmp\/mails<\/code><\/td>Local inspection<\/td><\/tr>
:test<\/code><\/td>Appends to ActionMailer::Base.deliveries<\/code><\/td>Automated tests<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
Underneath, ActionMailer uses the Mail gem to open the SMTP connection and speak the protocol. Rails does not deliver email itself \u2014 it hands a correctly formed message to whatever server you named.<\/p>\n\n\n\n
Why Rails Email Fails Silently in Production<\/h2>\n\n\n\n
\"Diagram
Four settings that let Rails report success while nothing is delivered.<\/figcaption><\/figure>\n\n\n\n
1. raise_delivery_errors Is Set to False<\/h3>\n\n\n\n
Rails’ generated development config sets raise_delivery_errors = false<\/code> so developers are not interrupted by mail failures while working offline. That block frequently gets copied into production.rb<\/code>.<\/p>\n\n\n\n
With it off, every SMTP exception is swallowed. Bad credentials, an unreachable host, a rejected recipient \u2014 all of it disappears. Your application reports success because, as far as it knows, nothing went wrong.<\/p>\n\n\n\n
2. perform_deliveries Is Disabled<\/h3>\n\n\n\n
Another development default. When false<\/code>, ActionMailer builds the message and discards it. The mailer runs, the view renders, and no connection is ever opened.<\/p>\n\n\n\n
3. deliver_later Uses the Async Adapter<\/h3>\n\n\n\n
Rails ships with the :async<\/code> queue adapter by default. It runs jobs on an in-process thread pool, which means queued email is held in memory. A deploy, a restart or a crash discards everything still waiting.<\/p>\n\n\n\n
For a password reset that is a lost login. For a receipt it is a support ticket.<\/p>\n\n\n\n
4. default_url_options Is Missing<\/h3>\n\n\n\n
Mailer views have no request context, so URL helpers cannot infer a host. Without default_url_options<\/code>, any mailer using a _url<\/code> helper raises Missing host to link to<\/code>. Under deliver_later<\/code> that surfaces as a failed job rather than a request error, which is easy to miss.<\/p>\n\n\n\n
5. No Authentication Records on the Sending Domain<\/h3>\n\n\n\n
Without SPF and DKIM, receiving servers cannot verify your application is authorised to send as your domain, in line with Google’s sender guidelines<\/a>. Our guide to SPF, DKIM and DMARC<\/a> covers the records, and the free email deliverability checker<\/a> shows what your domain currently publishes.<\/p>\n\n\n\n
Common Mistake<\/p>\n\n\n\n
Copying the ActionMailer block from development.rb<\/code> into production.rb<\/code>. That block exists to keep local development quiet, and it carries raise_delivery_errors = false<\/code> with it. In production the result is an application that cannot tell you its email is broken \u2014 the failure mode most likely to go unnoticed for weeks. Set it to true<\/code> in production, always.<\/p>\n\n\n\n
Quick Fix<\/p>\n\n\n\n
Rails Sends No Email in Production<\/p>\n\n\n\n