@Romance you need to add below code in the connect method
XMPPMessageDeliveryReceipts* xmppMessageDeliveryRecipts = [[XMPPMessageDeliveryReceipts alloc] initWithDispatchQueue:dispatch_get_main_queue()];
xmppMessageDeliveryRecipts.autoSendMessageDeliveryReceipts = YES;
xmppMessageDeliveryRecipts.autoSendMessageDeliveryRequests = YES;
[xmppMessageDeliveryRecipts activate:self.xmppStream];
Remember to add these line while sending message
NSString *messageID=[self.xmppStream generateUUID];
NSXMLElement *message = [NSXMLElement elementWithName:@"message"];
[message addAttributeWithName:@"id" stringValue:messageID];
[message addAttributeWithName:@"type" stringValue:@"chat"];
[message addAttributeWithName:@"to" stringValue:[NSString stringWithFormat:@"senderJabberID_Here"]];
[message addChild:body];
Hope this help you :)