diff --git a/pkg/runner/enumerate.go b/pkg/runner/enumerate.go
index f6ad34b63..0ba58b4e8 100644
--- a/pkg/runner/enumerate.go
+++ b/pkg/runner/enumerate.go
@@ -12,7 +12,7 @@ import (
 )
 
 // EnumerateSingleDomain performs subdomain enumeration against a single domain
-func (r *Runner) EnumerateSingleDomain(domain, output string) error {
+func (r *Runner) EnumerateSingleDomain(domain, output string, overwrite bool) error {
 	log.Infof("Enumerating subdomains for %s\n", domain)
 
 	// Get the API keys for sources from the configuration
@@ -127,10 +127,21 @@ func (r *Runner) EnumerateSingleDomain(domain, output string) error {
 			}
 		}
 
-		file, err := os.Create(output)
-		if err != nil {
-			log.Errorf("Could not create file %s for %s: %s\n", output, domain, err)
-			return err
+		var file *os.File
+		var err error
+
+		if overwrite {
+			file, err = os.Create(output)
+			if err != nil {
+				log.Errorf("Could not create file %s for %s: %s\n", output, domain, err)
+				return err
+			}
+		} else {
+			file, err = os.OpenFile(output, os.O_APPEND | os.O_CREATE | os.O_WRONLY, 0644)
+			if err != nil {
+				log.Errorf("Could not open file %s for %s: %s\n", output, domain, err)
+				return err
+			}
 		}
 
 		// Write the output to the file depending upon user requirement
diff --git a/pkg/runner/runner.go b/pkg/runner/runner.go
index 2dbfaa229..630857702 100644
--- a/pkg/runner/runner.go
+++ b/pkg/runner/runner.go
@@ -40,7 +40,7 @@ func NewRunner(options *Options) (*Runner, error) {
 func (r *Runner) RunEnumeration() error {
 	// Check if only a single domain is sent as input. Process the domain now.
 	if r.options.Domain != "" {
-		return r.EnumerateSingleDomain(r.options.Domain, r.options.Output)
+		return r.EnumerateSingleDomain(r.options.Domain, r.options.Output, true)
 	}
 
 	// If we have multiple domains as input,
@@ -65,17 +65,27 @@ func (r *Runner) RunEnumeration() error {
 // We keep enumerating subdomains for a given domain until we reach an error
 func (r *Runner) EnumerateMultipleDomains(reader io.Reader) error {
 	scanner := bufio.NewScanner(reader)
+	var scanned int = 0
 	for scanner.Scan() {
+		var isFirstRun bool = (scanned == 0)
+
 		domain := scanner.Text()
 		if domain == "" {
 			continue
 		}
 
-		outputFile := path.Join(r.options.OutputDirectory, domain)
-		err := r.EnumerateSingleDomain(domain, outputFile)
+		outputFile := ""
+		if r.options.Output != "" {
+			outputFile = path.Join(r.options.OutputDirectory, r.options.Output)
+		}
+
+		// the first enumeration will overwrite the output file,
+		// successive enumerations will append the results.
+		err := r.EnumerateSingleDomain(domain, outputFile, isFirstRun)
 		if err != nil {
 			return err
 		}
+		scanned++
 	}
 	return nil
 }