diff --git a/7_0/ch11/config/environments/production.rb b/7_0/ch11/config/environments/production.rb
index 8bc035b8..e801299d 100644
--- a/7_0/ch11/config/environments/production.rb
+++ b/7_0/ch11/config/environments/production.rb
@@ -71,7 +71,7 @@
   host = '<あなたのRenderアプリ名>.onrender.com'
   config.action_mailer.default_url_options = { host: host }
   ActionMailer::Base.smtp_settings = {
-    :port           => 587,
+    :port           => 2525,
     :address        => 'smtp.mailgun.org',
     :user_name      => ENV['MAILGUN_SMTP_LOGIN'],
     :password       => ENV['MAILGUN_SMTP_PASSWORD'],
diff --git a/7_0/ch12/config/environments/production.rb b/7_0/ch12/config/environments/production.rb
index 8bc035b8..e801299d 100644
--- a/7_0/ch12/config/environments/production.rb
+++ b/7_0/ch12/config/environments/production.rb
@@ -71,7 +71,7 @@
   host = '<あなたのRenderアプリ名>.onrender.com'
   config.action_mailer.default_url_options = { host: host }
   ActionMailer::Base.smtp_settings = {
-    :port           => 587,
+    :port           => 2525,
     :address        => 'smtp.mailgun.org',
     :user_name      => ENV['MAILGUN_SMTP_LOGIN'],
     :password       => ENV['MAILGUN_SMTP_PASSWORD'],
diff --git a/7_0/ch13/config/environments/production.rb b/7_0/ch13/config/environments/production.rb
index b124cdd6..7a9cc7e8 100644
--- a/7_0/ch13/config/environments/production.rb
+++ b/7_0/ch13/config/environments/production.rb
@@ -71,7 +71,7 @@
   host = '<あなたのRenderアプリ名>.onrender.com'
   config.action_mailer.default_url_options = { host: host }
   ActionMailer::Base.smtp_settings = {
-    :port           => 587,
+    :port           => 2525,
     :address        => 'smtp.mailgun.org',
     :user_name      => ENV['MAILGUN_SMTP_LOGIN'],
     :password       => ENV['MAILGUN_SMTP_PASSWORD'],
diff --git a/7_0/ch14/config/environments/production.rb b/7_0/ch14/config/environments/production.rb
index b124cdd6..7a9cc7e8 100644
--- a/7_0/ch14/config/environments/production.rb
+++ b/7_0/ch14/config/environments/production.rb
@@ -71,7 +71,7 @@
   host = '<あなたのRenderアプリ名>.onrender.com'
   config.action_mailer.default_url_options = { host: host }
   ActionMailer::Base.smtp_settings = {
-    :port           => 587,
+    :port           => 2525,
     :address        => 'smtp.mailgun.org',
     :user_name      => ENV['MAILGUN_SMTP_LOGIN'],
     :password       => ENV['MAILGUN_SMTP_PASSWORD'],