diff --git a/checker/collect.go b/checker/collect.go
index 8ec5c38..d675434 100644
--- a/checker/collect.go
+++ b/checker/collect.go
@@ -158,11 +158,7 @@ func loadConfig(opts sdk.CheckerOptions) (*runConfig, error) {
 		return nil, fmt.Errorf("smtp_host is required")
 	}
 	if cfg.FromAddress == "" {
-		domain := strings.TrimSpace(stringOpt(opts, "domain_name"))
-		if domain == "" {
-			return nil, fmt.Errorf("from_address is required when domain_name is not set")
-		}
-		cfg.FromAddress = "no-reply@" + strings.TrimSuffix(domain, ".")
+		return nil, fmt.Errorf("from_address is required")
 	}
 	parsedFrom, err := mail.ParseAddress(cfg.FromAddress)
 	if err != nil {
diff --git a/checker/definition.go b/checker/definition.go
index 787ff00..50d9612 100644
--- a/checker/definition.go
+++ b/checker/definition.go
@@ -35,6 +35,19 @@ func Definition() *sdk.CheckerDefinition {
 				},
 			},
 			UserOpts: []sdk.CheckerOptionDocumentation{
+				{
+					Id:          "happydeliver_url",
+					Type:        "string",
+					Label:       "happyDeliver instance URL (override)",
+					Description: "Override the operator-provided happyDeliver URL.",
+				},
+				{
+					Id:          "happydeliver_token",
+					Type:        "string",
+					Label:       "happyDeliver API token (override)",
+					Description: "Override the operator-provided happyDeliver token.",
+					Secret:      true,
+				},
 				{
 					Id:          "smtp_host",
 					Type:        "string",
@@ -71,6 +84,13 @@ func Definition() *sdk.CheckerDefinition {
 					Choices:     []string{"starttls", "tls", "none"},
 					Default:     "starttls",
 				},
+				{
+					Id:          "from_address",
+					Type:        "string",
+					Label:       "From address",
+					Description: "Address used in the From header of the test email. Must be in the tested domain.",
+					Required:    true,
+				},
 				{
 					Id:          "subject_override",
 					Type:        "string",
@@ -112,12 +132,6 @@ func Definition() *sdk.CheckerDefinition {
 					Label:    "Domain name",
 					AutoFill: sdk.AutoFillDomainName,
 				},
-				{
-					Id:          "from_address",
-					Type:        "string",
-					Label:       "From address",
-					Description: "Address used in the From header of the test email. Must be in the tested domain. Defaults to no-reply@<domain>.",
-				},
 			},
 		},
 		Rules: []sdk.CheckRule{