style(rubocop): Style/MutableConstant

app/models/smtp_endpoint.rb

@@ -26,7 +26,7 @@ class SMTPEndpoint < ApplicationRecord
   has_many :routes, as: :endpoint
   has_many :additional_route_endpoints, dependent: :destroy, as: :endpoint
 
-  SSL_MODES = ["None", "Auto", "STARTTLS", "TLS"]
+  SSL_MODES = ["None", "Auto", "STARTTLS", "TLS"].freeze
 
   before_destroy :update_routes