feat(mail): adds a test subcomand

pkg/config/config.go

@@ -20,6 +20,11 @@ type Config struct {
 	Providers       struct {
 		OVH *providerConfigs.OVHConfig `yaml:"ovh"`
 	} `yaml:"providers"`
+	Test *struct {
+		Address  string `yaml:"address"`
+		Username string `yaml:"username"`
+		Password string `yaml:"password"`
+	} `yaml:"test"`
 }
 
 func LoadConfig(path string) (*Config, error) {