checkAtsign method
Implementation
Future<bool> checkAtsign(String receiver) async {
// ignore: unnecessary_null_comparison
if (receiver == null) {
return false;
} else if (!receiver.contains('@')) {
receiver = '@' + receiver;
}
var checkPresence = await AtLookupImpl.findSecondary(
receiver, MixedConstants.ROOT_DOMAIN, 64);
return checkPresence != null;
}