diff --git a/gemfiles/Gemfile.actionmailer-3.0.x b/gemfiles/Gemfile.actionmailer-3.0.x
index 3773261..ed7cf53 100644
--- a/gemfiles/Gemfile.actionmailer-3.0.x
+++ b/gemfiles/Gemfile.actionmailer-3.0.x
@@ -1,6 +1,6 @@
 source "https://rubygems.org"
 
-gem 'postmark', '~> 1.4.0', :path => ENV['POSTMARK_GEM_PATH']
+gem 'postmark', '~> 1.5.0', :path => ENV['POSTMARK_GEM_PATH']
 gem 'actionmailer', '~> 3.0.0'
 
 group :test do
diff --git a/gemfiles/Gemfile.actionmailer-3.2.x b/gemfiles/Gemfile.actionmailer-3.2.x
index 56ab28e..137a096 100644
--- a/gemfiles/Gemfile.actionmailer-3.2.x
+++ b/gemfiles/Gemfile.actionmailer-3.2.x
@@ -1,6 +1,6 @@
 source "https://rubygems.org"
 
-gem 'postmark', '~> 1.4.0', :path => ENV['POSTMARK_GEM_PATH']
+gem 'postmark', '~> 1.5.0', :path => ENV['POSTMARK_GEM_PATH']
 gem 'actionmailer', '~> 3.2.0'
 gem 'i18n', '~> 0.6.0'
 
diff --git a/gemfiles/Gemfile.actionmailer-4.0.x b/gemfiles/Gemfile.actionmailer-4.0.x
index 840b084..925afc3 100644
--- a/gemfiles/Gemfile.actionmailer-4.0.x
+++ b/gemfiles/Gemfile.actionmailer-4.0.x
@@ -1,6 +1,6 @@
 source "https://rubygems.org"
 
-gem 'postmark', '~> 1.4.0', path: ENV['POSTMARK_GEM_PATH']
+gem 'postmark', '~> 1.5.0', path: ENV['POSTMARK_GEM_PATH']
 gem 'actionmailer', '~> 4.0.0'
 
 group :test do
diff --git a/gemfiles/Gemfile.actionmailer-4.1.x b/gemfiles/Gemfile.actionmailer-4.1.x
index 6e82470..d601b03 100644
--- a/gemfiles/Gemfile.actionmailer-4.1.x
+++ b/gemfiles/Gemfile.actionmailer-4.1.x
@@ -1,6 +1,6 @@
 source "https://rubygems.org"
 
-gem 'postmark', '~> 1.4.0', path: ENV['POSTMARK_GEM_PATH']
+gem 'postmark', '~> 1.5.0', path: ENV['POSTMARK_GEM_PATH']
 gem 'actionmailer', '~> 4.1.0'
 
 group :test do
diff --git a/gemfiles/Gemfile.actionmailer-4.2.x b/gemfiles/Gemfile.actionmailer-4.2.x
index 0835381..5d253c0 100644
--- a/gemfiles/Gemfile.actionmailer-4.2.x
+++ b/gemfiles/Gemfile.actionmailer-4.2.x
@@ -1,6 +1,6 @@
 source "https://rubygems.org"
 
-gem 'postmark', '~> 1.4.0', path: ENV['POSTMARK_GEM_PATH']
+gem 'postmark', '~> 1.5.0', path: ENV['POSTMARK_GEM_PATH']
 gem 'actionmailer', '~> 4.2.0'
 
 group :test do