What kinds of email accounts did you try? I didn't see such settings on ER6120. What's the model number indeed?

Did you try what bohemus suggests?

As I searched online, it seems that FI9821W has no PoE function. In this case, to power them on, you have to use SF1008P and POE10R.

There is a guide for you to configure VLAN which may help. http://www.tp-link.com/en/article/?faqid=544

Have you tried different ports on SW1 or different ethernet cables? It is suggested to connect SW2 to the UTM to see if the problem continues. If it just happens on SW1, it should be faulty. Get a...

Reset them. http://www.tp-link.com/en/article/?faqid=601 Pair them in the same room and move them to the proper location. http://www.tp-link.com/en/article/?faqid=258