diff --git a/.env_sample b/.env_sample
index 0645a5ca0..4ed89fac4 100644
--- a/.env_sample
+++ b/.env_sample
@@ -155,9 +155,13 @@ STACK_EXCHANGE_APP_KEY=""
 GITHUB_KEY="Optional"
 GITHUB_SECRET="Optional"
 
-# For Sendgrid email
-# https://sendgrid.com/docs/for-developers/sending-email/upgrade-your-authentication-method-to-api-keys/#upgrade-to-api-keys-for-your-smtp-integration
-SENDGRID_API_KEY="Optional, Production only"
+# For SMTP configuration
+SMTP_ADDRESS=
+SMTP_PORT=
+SMTP_DOMAIN=
+SMTP_USER_NAME=
+SMTP_PASSWORD=
+SMTP_AUTHENTICATION=
 
 
 # Disable simplecov coverage testing when running rspec locally
diff --git a/config/environments/development.rb b/config/environments/development.rb
index 26ff83cb1..407afbc72 100644
--- a/config/environments/development.rb
+++ b/config/environments/development.rb
@@ -14,8 +14,7 @@ Rails.application.configure do
   # Show full error reports.
   config.consider_all_requests_local = true
 
-  DEFAULT_EXPIRATION = 1.hour.to_i.freeze
-  config.cache_store = :redis_cache_store, { url: ENV["REDIS_URL"], expires_in: DEFAULT_EXPIRATION }
+  config.cache_store = :redis_cache_store, { url: ENV["REDIS_URL"], expires_in: 1.hour.to_i }
 
   # Enable/disable caching. By default caching is disabled.
   # Run rails dev:cache to toggle caching.
@@ -90,13 +89,12 @@ Rails.application.configure do
   config.action_mailer.perform_deliveries = true
   config.action_mailer.default_url_options = { host: config.app_domain }
   config.action_mailer.smtp_settings = {
-    address: "smtp.gmail.com",
-    port: "587",
-    enable_starttls_auto: true,
-    user_name: '<%= ENV["DEVELOPMENT_EMAIL_USERNAME"] %>',
-    password: '<%= ENV["DEVELOPMENT_EMAIL_PASSWORD"] %>',
-    authentication: :plain,
-    domain: config.app_domain
+    address: ENV["SMTP_ADDRESS"],
+    port: ENV["SMTP_PORT"],
+    authentication: ENV["SMTP_AUTHENTICATION"].presence || :plain,
+    user_name: ENV["SMTP_USER_NAME"],
+    password: ENV["SMTP_PASSWORD"],
+    domain: ENV["SMTP_DOMAIN"].presence || config.app_domain
   }
 
   config.action_mailer.preview_path = Rails.root.join("spec/mailers/previews")
diff --git a/config/environments/production.rb b/config/environments/production.rb
index 9a26dbf5c..efa428577 100644
--- a/config/environments/production.rb
+++ b/config/environments/production.rb
@@ -129,15 +129,25 @@ Rails.application.configure do
   config.action_mailer.delivery_method = :smtp
   config.action_mailer.perform_deliveries = true
   config.action_mailer.default_url_options = { host: protocol + ENV["APP_DOMAIN"].to_s }
-  ActionMailer::Base.smtp_settings = {
-    address: "smtp.sendgrid.net",
-    port: "587",
-    authentication: :plain,
-    user_name: "apikey",
-    password: ENV["SENDGRID_API_KEY"],
-    domain: ENV["APP_DOMAIN"],
-    enable_starttls_auto: true
-  }
+  ActionMailer::Base.smtp_settings = if ENV["SENDGRID_API_KEY"].present?
+                                       {
+                                         address: "smtp.sendgrid.net",
+                                         port: 587,
+                                         authentication: :plain,
+                                         user_name: "apikey",
+                                         password: ENV["SENDGRID_API_KEY"],
+                                         domain: ENV["APP_DOMAIN"]
+                                       }
+                                     else
+                                       {
+                                         address: ENV["SMTP_ADDRESS"],
+                                         port: ENV["SMTP_PORT"],
+                                         authentication: ENV["SMTP_AUTHENTICATION"],
+                                         user_name: ENV["SMTP_USER_NAME"],
+                                         password: ENV["SMTP_PASSWORD"],
+                                         domain: ENV["SMTP_DOMAIN"]
+                                       }
+                                     end
 
   if ENV["HEROKU_APP_URL"].present? && ENV["HEROKU_APP_URL"] != ENV["APP_DOMAIN"]
     config.middleware.use Rack::HostRedirect,
diff --git a/docs/backend/emails.md b/docs/backend/emails.md
index c9c2a5aa8..6ef137614 100644
--- a/docs/backend/emails.md
+++ b/docs/backend/emails.md
@@ -2,6 +2,24 @@
 title: Emails
 ---
 
+# Setting up email
+
+If you would like to enable transactional email using services like SendGrid or
+Mailgun, you can configure it by using the following environment variables:
+
+```shell
+SMTP_ADDRESS=         # ie. "smtp.sendgrid.net"
+SMTP_PORT=            # ie. 587
+SMTP_DOMAIN=
+SMTP_USER_NAME=
+SMTP_PASSWORD=
+SMTP_AUTHENTICATION=  # defaults to :plain
+```
+
+We follow the standard `ActionMailer` configuration. For more info, please check out
+Rails'
+[official documentation](https://guides.rubyonrails.org/action_mailer_basics.html#action-mailer-configuration).
+
 # Previewing emails in development
 
 You can view email previews at <http://localhost:3000/rails/mailers>.
@@ -10,4 +28,7 @@ Previews are setup in the directory `spec/mailers/previews`.
 
 # Overriding mailer templates
 
-To update the contents of emails that the app sends, edit the views under `app/views/mailers`. Note that this app uses the [`devise_invitable` gem](https://github.com/scambra/devise_invitable) for invitations. The views for this gem are stored under `app/views/devise/mailer`.
+To update the contents of emails that the app sends, edit the views under
+`app/views/mailers`. Note that this app uses the
+[`devise_invitable` gem](https://github.com/scambra/devise_invitable) for
+invitations. The views for this gem are stored under `app/views/devise/mailer`.