I posted earlier and got no response and just wanted to follow up once more.
I have RL-ARM TCPnet setup on a device and it only connects and sends and email via the SMTP functions about 50% of the time; all other times it comes back with SMTP_EVT_TIMEOUT or SMTP_EVT_ERROR as shown here: http://www.keil.com/support/man/docs/rlarm/rlarm_smtp_connect.htm
Unfortunately the descriptions of what those error mean is very lacking: in terms of what caused any possible timeout or protocol error.
The following page has a link for error functions but the link actually just takes you to the Ethernet functions page. http://www.keil.com/support/man/docs/rlarm/rlarm_tn_func_ref.htm
I have run Wireshark but the switch I'm using doesn't support port mirroring so I have no way to see the actual data entering and leaving the device and onto the network. I can however see the DHCP request, offer, ack etc.
If anyone has used the TCPnet libraries before and has had any experience with the SMTP functionality, any help is appreciated.
No - switches do not send all packets to all ports. If they did, then they wouldn't be switches but stupid hubs.
But supervised switches often have an administrative interface where an administrator can configure that he wants all traffic on port "n" to be duplicated on a dedicated monitor port, where he can connect a tcp-dump application and analyze exactly what happens on port "n".