feat: Support Azure single-tenant application using the Graph API (#6728) (#6878)

app/mailers/conversation_reply_mailer_helper.rb

@@ -23,6 +23,7 @@ module ConversationReplyMailerHelper
 
   def ms_smtp_settings
     return unless @inbox.email? && @channel.imap_enabled && @inbox.channel.provider == 'microsoft'
+    return ms_graph_settings if ENV.fetch('AZURE_TENANT_ID', false)
 
     smtp_settings = {
       address: 'smtp.office365.com',
@@ -40,6 +41,15 @@ module ConversationReplyMailerHelper
     @options[:delivery_method_options] = smtp_settings
   end
 
+  def ms_graph_settings
+    graph_settings = {
+      token: @channel.provider_config['access_token']
+    }
+
+    @options[:delivery_method] = :microsoft_graph
+    @options[:delivery_method_options] = graph_settings
+  end
+
   def set_delivery_method
     return unless @inbox.inbox_type == 'Email' && @channel.smtp_enabled