diff --git a/main.go b/main.go
index 7cf5777..a163c9b 100644
--- a/main.go
+++ b/main.go
@@ -23,12 +23,13 @@ var (
 	htpasswdFile            = flag.String("htpasswd-file", "", "additionally authenticate against a htpasswd file. Entries must be created with \"htpasswd -s\" for SHA encryption")
 	cookieSecret            = flag.String("cookie-secret", "", "the seed string for secure cookies")
 	cookieDomain            = flag.String("cookie-domain", "", "an optional cookie domain to force cookies to")
-	googleAppsDomain        = flag.String("google-apps-domain", "", "authenticate against the given google apps domain")
 	authenticatedEmailsFile = flag.String("authenticated-emails-file", "", "authenticate against emails via file (one per line)")
+	googleAppsDomains       = StringArray{}
 	upstreams               = StringArray{}
 )
 
 func init() {
+	flag.Var(&googleAppsDomains, "google-apps-domain", "authenticate against the given google apps domain (may be given multiple times)")
 	flag.Var(&upstreams, "upstream", "the http url(s) of the upstream endpoint. If multiple, routing is based on path")
 }
 
@@ -78,11 +79,11 @@ func main() {
 		log.Fatalf("error parsing --redirect-url %s", err.Error())
 	}
 
-	validator := NewValidator(*googleAppsDomain, *authenticatedEmailsFile)
+	validator := NewValidator(googleAppsDomains, *authenticatedEmailsFile)
 	oauthproxy := NewOauthProxy(upstreamUrls, *clientID, *clientSecret, validator)
 	oauthproxy.SetRedirectUrl(redirectUrl)
-	if *googleAppsDomain != "" && *authenticatedEmailsFile == "" {
-		oauthproxy.SignInMessage = fmt.Sprintf("using a %s email address", *googleAppsDomain)
+	if len(googleAppsDomains) != 0 && *authenticatedEmailsFile == "" {
+		oauthproxy.SignInMessage = fmt.Sprintf("using a email address from the following domains: %v", strings.Join(googleAppsDomains, ", "))
 	}
 	if *htpasswdFile != "" {
 		oauthproxy.HtpasswdFile, err = NewHtpasswdFromFile(*htpasswdFile)
diff --git a/validator.go b/validator.go
index bf07ea5..4caa5ec 100644
--- a/validator.go
+++ b/validator.go
@@ -8,13 +8,8 @@ import (
 	"strings"
 )
 
-func NewValidator(domain string, usersFile string) func(string) bool {
-
+func NewValidator(domains []string, usersFile string) func(string) bool {
 	validUsers := make(map[string]bool)
-	emailSuffix := ""
-	if domain != "" {
-		emailSuffix = fmt.Sprintf("@%s", domain)
-	}
 
 	if usersFile != "" {
 		r, err := os.Open(usersFile)
@@ -32,9 +27,10 @@ func NewValidator(domain string, usersFile string) func(string) bool {
 	}
 
 	validator := func(email string) bool {
-		var valid bool
-		if emailSuffix != "" {
-			valid = strings.HasSuffix(email, emailSuffix)
+		valid := false
+		for _, domain := range domains {
+			emailSuffix := fmt.Sprintf("@%s", domain)
+			valid = valid || strings.HasSuffix(email, emailSuffix)
 		}
 		if !valid {
 			_, valid = validUsers[email]