refactor: refactor the SMTP sender

config/initializers/inflections.rb

@@ -21,6 +21,7 @@ ActiveSupport::Inflector.inflections(:en) do |inflect|
 
   inflect.acronym "API"
   inflect.acronym "DNS"
+  inflect.acronym "SSL"
   inflect.acronym "MySQL"
 
   inflect.acronym "DB"

config/initializers/smtp_extensions.rb

@@ -6,6 +6,8 @@ module Net
     attr_accessor :source_address
 
     def secure_socket?
+      return false unless @socket
+
       @socket.io.is_a?(OpenSSL::SSL::SSLSocket)
     end