In general, are there only three queues? If so, I would recommend using tags instead of a metric.

```
postfix.queue.size{queue:active}
postfix.queue.size{queue:incoming}
postfix.queue.size{queue:deferred}
```

This make it much easier to graph in Datadog. For example, it's very simple to graph the size of all queues in one graph statement vs. one for each queue. For example:

```
sum:postfix.queue.size{role:email-server} by {queue}
```