diff --git a/api/agent.go b/api/agent.go
index 87016eeb7..422d06259 100644
--- a/api/agent.go
+++ b/api/agent.go
@@ -494,15 +494,13 @@ func getUserCredentials(usersFilePath string, _ *loadtest.Config) ([]user, error
 		password := split[1]
 		// Quick and dirty hack to extract username from email.
 		// This is not terribly important to be correct.
-		username := strings.Split(email, "@")[0]
-		username = strings.Replace(username, "+", "-", -1)
 		authService := userentity.AuthenticationTypeMattermost
 
 		// Check if the user has a custom authentication type. Custom authentication types are
 		// specified by prepending the email with the authentication type followed by a colon.
 		// Example: "openid:email1@xample.com"
-		if strings.Contains(username, ":") {
-			split := strings.Split(username, ":")
+		if strings.Contains(email, ":") {
+			split := strings.Split(email, ":")
 			if len(split) != 2 {
 				return nil, fmt.Errorf("invalid custom authentication found in %q", email)
 			}
@@ -515,10 +513,16 @@ func getUserCredentials(usersFilePath string, _ *loadtest.Config) ([]user, error
 				return nil, fmt.Errorf("invalid custom authentication type %q", authService)
 			}
 
-			username = split[1]
 			email = strings.Replace(email, authService+":", "", 1)
 		}
 
+		emailParts := strings.Split(email, "@")
+		if len(emailParts) != 2 {
+			return nil, fmt.Errorf("invalid email %q", email)
+		}
+
+		username := emailParts[0]
+
 		users = append(users, user{
 			email:       email,
 			username:    username,
diff --git a/loadtest/user/userentity/actions.go b/loadtest/user/userentity/actions.go
index 0f4a43667..5183ad9c6 100644
--- a/loadtest/user/userentity/actions.go
+++ b/loadtest/user/userentity/actions.go
@@ -47,9 +47,9 @@ func (ue *UserEntity) SignUp(email, username, password string) error {
 			return fmt.Errorf("error while signing up using %s: %w", ue.config.AuthenticationType, err)
 		}
 
-		newUser, _, err = ue.client.GetUserByUsername(context.Background(), username, "")
+		newUser, _, err = ue.client.GetUserByEmail(context.Background(), email, "")
 		if err != nil {
-			return fmt.Errorf("error while getting user by username: %w", err)
+			return fmt.Errorf("error while getting user by email: %w", err)
 		}
 
 	default:
@@ -194,9 +194,9 @@ func (ue *UserEntity) Login() error {
 			return fmt.Errorf("error while logging in using %s: %w", ue.config.AuthenticationType, err)
 		}
 
-		loggedUser, _, err = ue.client.GetUserByUsername(context.Background(), user.Username, "")
+		loggedUser, _, err = ue.client.GetUserByEmail(context.Background(), user.Email, "")
 		if err != nil {
-			return fmt.Errorf("error while getting user by username through %s: %w", ue.config.AuthenticationType, err)
+			return fmt.Errorf("error while getting user by email through %s: %w", ue.config.AuthenticationType, err)
 		}
 	default:
 		loggedUser, _, err = ue.client.Login(context.Background(), user.Email, user.Password)