There are several ways to view who's on your network, some easier/less technical than others:


The logging feature in your router;
Sometimes you can view currently connected devices. For example in a FritzBox you can see all devices that have a dhcp lease (i.e. which got an IP address) on the "Home Network" page.
You could scan the network from your laptop using a tool like Zenmap (or Nmap on the command line).
A bit more advanced, but you can also put your WiFi card in monitor mode and look for devices that communicate with your access point. Wireshark and airmon-ng are the tools I would use, but there may be better options.
If you have shell access to your router, you could use netstat or even tcpdump to view connections and traffic.
You could turn off DHCP on your router and enable it on your laptop, so that you can easily see who is trying to get a lease.
Using Wireshark you can see broadcasts on the network. Almost every device broadcasts something from time to time so if your access point works as a switch (i.e. if wireless clients can reach each other on layer 2 (ethernet)) you can pretty easily enumerate all active MAC addresses.


WiFi connection history
I'm looking to replace our current use of an external smtp provider with an in-house installation. It should handle the following situations:


Certain addresses should be forwarded to gmail addresses; we'd like to continue to use gmail as our primary email interface.
Other addresses should be available as pop/imap mailboxes.
Other addresses will be handled programmatically: they'll kick off various tasks, get logged, etc. These addresses should either kick off a process to the handle the email addresses, or should store in an easily processable format.
It should also be fairly easily configurable with domain keys, spf, and anything else it takes to allow email deliverability.


I've used sendmail in the distant past. It seems postfix and exim are the recommended options these days. My main question is: what's the best choice and setup for the forwarding of the addresses to gmail, and for the programmatic access? Is procmail still the way to go or are there better options these days?

We're using linux/ubuntu servers.
