diff --git a/app/controllers/spree/admin/orders_controller.rb b/app/controllers/spree/admin/orders_controller.rb
index 5fa22fd0a1..38da5e812e 100644
--- a/app/controllers/spree/admin/orders_controller.rb
+++ b/app/controllers/spree/admin/orders_controller.rb
@@ -78,7 +78,7 @@ module Spree
       end
 
       def resend
-        Spree::OrderMailer.confirm_email_for_customer(@order.id, true).deliver_now
+        Spree::OrderMailer.confirm_email_for_customer(@order.id, true).deliver_later
         flash[:success] = t('admin.orders.order_email_resent')
 
         respond_with(@order) { |format| format.html { redirect_to :back } }
@@ -87,7 +87,7 @@ module Spree
       def invoice
         pdf = InvoiceRenderer.new.render_to_string(@order)
 
-        Spree::OrderMailer.invoice_email(@order.id, pdf).deliver_now
+        Spree::OrderMailer.invoice_email(@order.id, pdf).deliver_later
         flash[:success] = t('admin.orders.invoice_email_sent')
 
         respond_with(@order) { |format|
diff --git a/app/models/spree/order.rb b/app/models/spree/order.rb
index 55aee6e85b..4649b5a0e6 100644
--- a/app/models/spree/order.rb
+++ b/app/models/spree/order.rb
@@ -824,7 +824,7 @@ module Spree
     def after_cancel
       shipments.each(&:cancel!)
 
-      OrderMailer.cancel_email(id).deliver_now
+      OrderMailer.cancel_email(id).deliver_later
       self.payment_state = 'credit_owed' unless shipped?
     end
 
diff --git a/app/models/spree/shipment.rb b/app/models/spree/shipment.rb
index 10309bb156..e706c3dbac 100644
--- a/app/models/spree/shipment.rb
+++ b/app/models/spree/shipment.rb
@@ -319,7 +319,7 @@ module Spree
     end
 
     def send_shipped_email
-      ShipmentMailer.shipped_email(id).deliver_now
+      ShipmentMailer.shipped_email(id).deliver_later
     end
 
     def update_adjustment_included_tax
diff --git a/engines/order_management/app/services/order_management/subscriptions/summarizer.rb b/engines/order_management/app/services/order_management/subscriptions/summarizer.rb
index fe02a9ad9c..24221c9c38 100644
--- a/engines/order_management/app/services/order_management/subscriptions/summarizer.rb
+++ b/engines/order_management/app/services/order_management/subscriptions/summarizer.rb
@@ -37,13 +37,13 @@ module OrderManagement
 
       def send_placement_summary_emails
         @summaries.values.each do |summary|
-          SubscriptionMailer.placement_summary_email(summary).deliver_now
+          SubscriptionMailer.placement_summary_email(summary).deliver_later
         end
       end
 
       def send_confirmation_summary_emails
         @summaries.values.each do |summary|
-          SubscriptionMailer.confirmation_summary_email(summary).deliver_now
+          SubscriptionMailer.confirmation_summary_email(summary).deliver_later
         end
       end
 
diff --git a/engines/order_management/spec/services/order_management/subscriptions/summarizer_spec.rb b/engines/order_management/spec/services/order_management/subscriptions/summarizer_spec.rb
index 0c47277e47..f0d8f9dbe0 100644
--- a/engines/order_management/spec/services/order_management/subscriptions/summarizer_spec.rb
+++ b/engines/order_management/spec/services/order_management/subscriptions/summarizer_spec.rb
@@ -100,7 +100,7 @@ module OrderManagement
         let(:summary1) { double(:summary) }
         let(:summary2) { double(:summary) }
         let(:summaries) { { 1 => summary1, 2 => summary2 } }
-        let(:mail_mock) { double(:mail, deliver_now: true) }
+        let(:mail_mock) { double(:mail, deliver_later: true) }
 
         before do
           summarizer.instance_variable_set(:@summaries, summaries)
@@ -116,7 +116,7 @@ module OrderManagement
         let(:summary1) { double(:summary) }
         let(:summary2) { double(:summary) }
         let(:summaries) { { 1 => summary1, 2 => summary2 } }
-        let(:mail_mock) { double(:mail, deliver_now: true) }
+        let(:mail_mock) { double(:mail, deliver_later: true) }
 
         before do
           summarizer.instance_variable_set(:@summaries, summaries)
diff --git a/spec/controllers/admin/proxy_orders_controller_spec.rb b/spec/controllers/admin/proxy_orders_controller_spec.rb
index 7c06b6eeb1..46436dedda 100644
--- a/spec/controllers/admin/proxy_orders_controller_spec.rb
+++ b/spec/controllers/admin/proxy_orders_controller_spec.rb
@@ -78,7 +78,7 @@ describe Admin::ProxyOrdersController, type: :controller do
 
     before do
       # Processing order to completion
-      allow(Spree::OrderMailer).to receive(:cancel_email) { double(:email, deliver_now: true) }
+      allow(Spree::OrderMailer).to receive(:cancel_email) { double(:email, deliver_later: true) }
       OrderWorkflow.new(order).complete!
       proxy_order.reload
       proxy_order.cancel
diff --git a/spec/controllers/admin/subscriptions_controller_spec.rb b/spec/controllers/admin/subscriptions_controller_spec.rb
index ec88c10bae..4ef466f3e1 100644
--- a/spec/controllers/admin/subscriptions_controller_spec.rb
+++ b/spec/controllers/admin/subscriptions_controller_spec.rb
@@ -446,7 +446,7 @@ describe Admin::SubscriptionsController, type: :controller do
               before do
                 params[:open_orders] = 'cancel'
                 allow(Spree::OrderMailer).to receive(:cancel_email) { mail_mock }
-                allow(mail_mock).to receive(:deliver_now)
+                allow(mail_mock).to receive(:deliver_later)
               end
 
               it 'renders the cancelled subscription as json, and cancels the open order' do
@@ -457,7 +457,7 @@ describe Admin::SubscriptionsController, type: :controller do
                 expect(subscription.reload.canceled_at).to be_within(5.seconds).of Time.zone.now
                 expect(order.reload.state).to eq 'canceled'
                 expect(proxy_order.reload.canceled_at).to be_within(5.seconds).of Time.zone.now
-                expect(mail_mock).to have_received(:deliver_now)
+                expect(mail_mock).to have_received(:deliver_later)
               end
             end
           end
@@ -545,7 +545,7 @@ describe Admin::SubscriptionsController, type: :controller do
               before do
                 params[:open_orders] = 'cancel'
                 allow(Spree::OrderMailer).to receive(:cancel_email) { mail_mock }
-                allow(mail_mock).to receive(:deliver_now)
+                allow(mail_mock).to receive(:deliver_later)
               end
 
               it 'renders the paused subscription as json, and cancels the open order' do
@@ -556,7 +556,7 @@ describe Admin::SubscriptionsController, type: :controller do
                 expect(subscription.reload.paused_at).to be_within(5.seconds).of Time.zone.now
                 expect(order.reload.state).to eq 'canceled'
                 expect(proxy_order.reload.canceled_at).to be_within(5.seconds).of Time.zone.now
-                expect(mail_mock).to have_received(:deliver_now)
+                expect(mail_mock).to have_received(:deliver_later)
               end
             end
           end
diff --git a/spec/controllers/spree/admin/orders_controller_spec.rb b/spec/controllers/spree/admin/orders_controller_spec.rb
index 301dea10c4..817e1c3b3a 100644
--- a/spec/controllers/spree/admin/orders_controller_spec.rb
+++ b/spec/controllers/spree/admin/orders_controller_spec.rb
@@ -170,17 +170,20 @@ describe Spree::Admin::OrdersController, type: :controller do
         end
 
         context "when the distributor's ABN has been set" do
-          before { distributor.update_attribute(:abn, "123") }
+          let(:mail_mock) { double(:mailer_mock, deliver_later: true) }
+
           before do
-            ActionMailer::Base.perform_deliveries = true
+            allow(Spree::OrderMailer).to receive(:invoice_email) { mail_mock }
+            distributor.update_attribute(:abn, "123")
             setup_email
           end
 
           it "should allow me to send order invoices" do
-            expect do
-              spree_get :invoice, params
-            end.to change{ Spree::OrderMailer.deliveries.count }.by(1)
+            spree_get :invoice, params
+
             expect(response).to redirect_to spree.edit_admin_order_path(order)
+            expect(Spree::OrderMailer).to have_received(:invoice_email)
+            expect(mail_mock).to have_received(:deliver_later)
           end
         end
       end
diff --git a/spec/models/proxy_order_spec.rb b/spec/models/proxy_order_spec.rb
index 76fe554016..fc6ccf9810 100644
--- a/spec/models/proxy_order_spec.rb
+++ b/spec/models/proxy_order_spec.rb
@@ -30,7 +30,7 @@ describe ProxyOrder, type: :model do
         let(:order) { create(:completed_order_with_totals) }
 
         it "returns true and sets canceled_at to the current time, and cancels the order" do
-          expect(Spree::OrderMailer).to receive(:cancel_email) { double(:email, deliver_now: true) }
+          expect(Spree::OrderMailer).to receive(:cancel_email) { double(:email, deliver_later: true) }
           expect(proxy_order.cancel).to be true
           expect_cancelled_now proxy_order
           expect(order.reload.state).to eq 'canceled'
@@ -107,7 +107,7 @@ describe ProxyOrder, type: :model do
 
       context "and the order has already been cancelled" do
         before do
-          allow(Spree::OrderMailer).to receive(:cancel_email) { double(:email, deliver_now: true) }
+          allow(Spree::OrderMailer).to receive(:cancel_email) { double(:email, deliver_later: true) }
           while !order.completed? do break unless order.next! end
           order.cancel
         end
@@ -147,7 +147,7 @@ describe ProxyOrder, type: :model do
 
       context "and the order has been cancelled" do
         before do
-          allow(Spree::OrderMailer).to receive(:cancel_email) { double(:email, deliver_now: true) }
+          allow(Spree::OrderMailer).to receive(:cancel_email) { double(:email, deliver_later: true) }
           while !order.completed? do break unless order.next! end
           order.cancel
         end
diff --git a/spec/models/spree/order/state_machine_spec.rb b/spec/models/spree/order/state_machine_spec.rb
index bc7177907f..ce59e1b212 100644
--- a/spec/models/spree/order/state_machine_spec.rb
+++ b/spec/models/spree/order/state_machine_spec.rb
@@ -123,7 +123,7 @@ describe Spree::Order do
         order_id = args[0]
         mail_message
       }
-      expect(mail_message).to receive :deliver_now
+      expect(mail_message).to receive :deliver_later
       order.cancel!
       expect(order_id).to eq order.id
     end
@@ -133,7 +133,7 @@ describe Spree::Order do
         allow(shipment).to receive(:ensure_correct_adjustment)
         allow(shipment).to receive(:update_order)
         allow(Spree::OrderMailer).to receive(:cancel_email).and_return(mail_message = double)
-        allow(mail_message).to receive :deliver_now
+        allow(mail_message).to receive :deliver_later
 
         allow(order).to receive :has_available_shipment
       end
@@ -143,7 +143,7 @@ describe Spree::Order do
       before do
         # Stubs methods that cause unwanted side effects in this test
         allow(Spree::OrderMailer).to receive(:cancel_email).and_return(mail_message = double)
-        allow(mail_message).to receive :deliver_now
+        allow(mail_message).to receive :deliver_later
         allow(order).to receive :has_available_shipment
         allow(order).to receive :restock_items!
         allow(shipment).to receive(:cancel!)
diff --git a/spec/models/spree/order_spec.rb b/spec/models/spree/order_spec.rb
index 85ed732112..2361ff3a21 100644
--- a/spec/models/spree/order_spec.rb
+++ b/spec/models/spree/order_spec.rb
@@ -179,7 +179,7 @@ describe Spree::Order do
       # Stub this method as it's called due to a callback
       # and it's irrelevant to this test
       allow(order).to receive :has_available_shipment
-      allow(Spree::OrderMailer).to receive_message_chain :confirm_email, :deliver_now
+      allow(Spree::OrderMailer).to receive_message_chain :confirm_email, :deliver_later
       adjustments = double
       allow(order).to receive_messages adjustments: adjustments
       expect(adjustments).to receive(:update_all).with(state: 'closed')
diff --git a/spec/models/spree/shipment_spec.rb b/spec/models/spree/shipment_spec.rb
index 6e2758c153..991bba405b 100644
--- a/spec/models/spree/shipment_spec.rb
+++ b/spec/models/spree/shipment_spec.rb
@@ -376,7 +376,7 @@ describe Spree::Shipment do
         shipment_id = args[0]
         mail_message
       }
-      expect(mail_message).to receive :deliver_now
+      expect(mail_message).to receive :deliver_later
       shipment.ship!
       expect(shipment_id).to eq shipment.id
     end