diff --git a/lib/mail_handler/backends/mail_backend.rb b/lib/mail_handler/backends/mail_backend.rb
index ae1f79307e4..9354f9ff882 100644
--- a/lib/mail_handler/backends/mail_backend.rb
+++ b/lib/mail_handler/backends/mail_backend.rb
@@ -399,19 +399,12 @@ def address_from_string(string)
       end
 
       def get_emails_within_received_headers(email)
-        received_addresses = []
-        received_headers = email['Received']
-        if received_headers
-          if received_headers.class == Mail::Field
-            received_header_string = received_headers.to_s
-          else
-            received_header_string = received_headers.
-              map { | header | header.to_s } * ' '
-          end
-          received_addresses = received_header_string.
-            scan(MySociety::Validate.email_find_regexp).flatten
-        end
-        received_addresses
+        received_headers = Array(email['Received'])
+        return [] if received_headers.empty?
+        received_headers.map(&:to_s).
+          join(' ').
+          scan(MySociety::Validate.email_find_regexp).
+          flatten
       end
     end
   end