diff --git a/oidc.go b/oidc.go
index a47863ff..495832a5 100644
--- a/oidc.go
+++ b/oidc.go
@@ -9,7 +9,6 @@ import (
 	"fmt"
 	"html/template"
 	"net/http"
-	"regexp"
 	"strings"
 	"time"
 
@@ -282,109 +281,90 @@ func (h *Headscale) OIDCCallback(ctx *gin.Context) {
 
 	now := time.Now().UTC()
 
-	if namespaceName, ok := h.getNamespaceFromEmail(claims.Email); ok {
-		// register the machine if it's new
-		if !machine.Registered {
-			log.Debug().Msg("Registering new machine after successful callback")
-
-			namespace, err := h.GetNamespace(namespaceName)
-			if errors.Is(err, gorm.ErrRecordNotFound) {
-				namespace, err = h.CreateNamespace(namespaceName)
-
-				if err != nil {
-					log.Error().
-						Err(err).
-						Caller().
-						Msgf("could not create new namespace '%s'", namespaceName)
-					ctx.String(
-						http.StatusInternalServerError,
-						"could not create new namespace",
-					)
-
-					return
-				}
-			} else if err != nil {
-				log.Error().
-					Caller().
-					Err(err).
-					Str("namespace", namespaceName).
-					Msg("could not find or create namespace")
-				ctx.String(
-					http.StatusInternalServerError,
-					"could not find or create namespace",
-				)
-
-				return
-			}
-
-			ips, err := h.getAvailableIPs()
-			if err != nil {
-				log.Error().
-					Caller().
-					Err(err).
-					Msg("could not get an IP from the pool")
-				ctx.String(
-					http.StatusInternalServerError,
-					"could not get an IP from the pool",
-				)
-
-				return
-			}
-
-			machine.IPAddresses = ips
-			machine.NamespaceID = namespace.ID
-			machine.Registered = true
-			machine.RegisterMethod = RegisterMethodOIDC
-			machine.LastSuccessfulUpdate = &now
-			machine.Expiry = &requestedTime
-			h.db.Save(&machine)
-		}
-
-		var content bytes.Buffer
-		if err := oidcCallbackTemplate.Execute(&content, oidcCallbackTemplateConfig{
-			User: claims.Email,
-			Verb: "Authenticated",
-		}); err != nil {
-			log.Error().
-				Str("func", "OIDCCallback").
-				Str("type", "authenticate").
-				Err(err).
-				Msg("Could not render OIDC callback template")
-			ctx.Data(
-				http.StatusInternalServerError,
-				"text/html; charset=utf-8",
-				[]byte("Could not render OIDC callback template"),
-			)
-		}
-
-		ctx.Data(http.StatusOK, "text/html; charset=utf-8", content.Bytes())
-
+	namespaceName, err := NormalizeNamespaceName(claims.Email)
+	if err != nil {
+		log.Error().Err(err).Caller().Msgf("couldn't normalize email")
+		ctx.String(
+			http.StatusInternalServerError,
+			"couldn't normalize email",
+		)
 		return
 	}
+	// register the machine if it's new
+	if !machine.Registered {
+		log.Debug().Msg("Registering new machine after successful callback")
 
-	log.Error().
-		Caller().
-		Str("email", claims.Email).
-		Str("username", claims.Username).
-		Str("machine", machine.Name).
-		Msg("Email could not be mapped to a namespace")
-	ctx.String(
-		http.StatusBadRequest,
-		"email from claim could not be mapped to a namespace",
-	)
-}
+		namespace, err := h.GetNamespace(namespaceName)
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			namespace, err = h.CreateNamespace(namespaceName)
 
-// getNamespaceFromEmail passes the users email through a list of "matchers"
-// and iterates through them until it matches and returns a namespace.
-// If no match is found, an empty string will be returned.
-// TODO(kradalby): golang Maps key order is not stable, so this list is _not_ deterministic. Find a way to make the list of keys stable, preferably in the order presented in a users configuration.
-func (h *Headscale) getNamespaceFromEmail(email string) (string, bool) {
-	for match, namespace := range h.cfg.OIDC.MatchMap {
-		regex := regexp.MustCompile(match)
-		if regex.MatchString(email) {
-			return namespace, true
+			if err != nil {
+				log.Error().
+					Err(err).
+					Caller().
+					Msgf("could not create new namespace '%s'", namespaceName)
+				ctx.String(
+					http.StatusInternalServerError,
+					"could not create new namespace",
+				)
+
+				return
+			}
+		} else if err != nil {
+			log.Error().
+				Caller().
+				Err(err).
+				Str("namespace", namespaceName).
+				Msg("could not find or create namespace")
+			ctx.String(
+				http.StatusInternalServerError,
+				"could not find or create namespace",
+			)
+
+			return
 		}
+
+		ips, err := h.getAvailableIPs()
+		if err != nil {
+			log.Error().
+				Caller().
+				Err(err).
+				Msg("could not get an IP from the pool")
+			ctx.String(
+				http.StatusInternalServerError,
+				"could not get an IP from the pool",
+			)
+
+			return
+		}
+
+		machine.IPAddresses = ips
+		machine.NamespaceID = namespace.ID
+		machine.Registered = true
+		machine.RegisterMethod = RegisterMethodOIDC
+		machine.LastSuccessfulUpdate = &now
+		machine.Expiry = &requestedTime
+		h.db.Save(&machine)
 	}
 
-	return "", false
+	var content bytes.Buffer
+	if err := oidcCallbackTemplate.Execute(&content, oidcCallbackTemplateConfig{
+		User: claims.Email,
+		Verb: "Authenticated",
+	}); err != nil {
+		log.Error().
+			Str("func", "OIDCCallback").
+			Str("type", "authenticate").
+			Err(err).
+			Msg("Could not render OIDC callback template")
+		ctx.Data(
+			http.StatusInternalServerError,
+			"text/html; charset=utf-8",
+			[]byte("Could not render OIDC callback template"),
+		)
+	}
+
+	ctx.Data(http.StatusOK, "text/html; charset=utf-8", content.Bytes())
+
+	return
 }