%{auth_domain} shouldn't include the leading '@'

src/imap-hibernate/imap-client.c

@@ -485,6 +485,7 @@ imap_client_get_var_expand_table(struct imap_client *client)
 		tab[11].value = auth_user;
 		tab[12].value = t_strcut(auth_user, '@');
 		tab[13].value = strchr(auth_user, '@');
+		if (tab[13].value != NULL) tab[13].value++;
 	}
 	return tab;
 }

src/lib-storage/mail-storage-service.c

@@ -436,6 +436,7 @@ get_var_expand_table(struct master_service *service,
 		tab[10].value = user->auth_user;
 		tab[11].value = t_strcut(user->auth_user, '@');
 		tab[12].value = strchr(user->auth_user, '@');
+		if (tab[12].value != NULL) tab[12].value++;
 	}
 	return tab;
 }

src/lib-storage/mail-user.c

@@ -260,6 +260,7 @@ mail_user_var_expand_table(struct mail_user *user)
 		tab[11].value = user->auth_user;
 		tab[12].value = p_strdup(user->pool, t_strcut(user->auth_user, '@'));
 		tab[13].value = strchr(user->auth_user, '@');
+		if (tab[13].value != NULL) tab[13].value++;
 	}
 
 	user->var_expand_table = tab;