diff --git a/validator.go b/validator.go
index 81a1bf8..f85e1d4 100644
--- a/validator.go
+++ b/validator.go
@@ -23,11 +23,16 @@ func NewValidator(domains []string, usersFile string) func(string) bool {
 		csv_reader.TrimLeadingSpace = true
 		records, err := csv_reader.ReadAll()
 		for _, r := range records {
-			validUsers[r[0]] = true
+			validUsers[strings.ToLower(r[0])] = true
 		}
 	}
 
+	for i, domain := range domains {
+		domains[i] = strings.ToLower(domain)
+	}
+
 	validator := func(email string) bool {
+		email = strings.ToLower(email)
 		valid := false
 		for _, domain := range domains {
 			emailSuffix := fmt.Sprintf("@%s", domain)
diff --git a/validator_test.go b/validator_test.go
new file mode 100644
index 0000000..3c223bd
--- /dev/null
+++ b/validator_test.go
@@ -0,0 +1,40 @@
+package main
+
+import (
+	"io/ioutil"
+	"os"
+	"strings"
+	"testing"
+)
+
+func TestValidatorComparisonsAreCaseInsensitive(t *testing.T) {
+	auth_email_file, err := ioutil.TempFile("", "test_auth_emails_")
+	if err != nil {
+		t.Fatal("failed to create temp file: " + err.Error())
+	}
+	defer os.Remove(auth_email_file.Name())
+
+	auth_email_file.WriteString(
+		strings.Join([]string{"Foo.Bar@Example.Com"}, "\n"))
+	err = auth_email_file.Close()
+	if err != nil {
+		t.Fatal("failed to close temp file " + auth_email_file.Name() +
+			": " + err.Error())
+	}
+
+	domains := []string{"Frobozz.Com"}
+	validator := NewValidator(domains, auth_email_file.Name())
+
+	if !validator("foo.bar@example.com") {
+		t.Error("loaded email addresses are not lower-cased")
+	}
+	if !validator("Foo.Bar@Example.Com") {
+		t.Error("validated email addresses are not lower-cased")
+	}
+	if !validator("foo.bar@frobozz.com") {
+		t.Error("loaded domains are not lower-cased")
+	}
+	if !validator("foo.bar@Frobozz.Com") {
+		t.Error("validated domains are not lower-cased")
+	}
+}