@David-TP 

hi. I had tried this previously by removing the old Main deco. 
I have now removed both M5s from the network and did still get a couple of alerts. Then it went quiet so I added the M5s back one at a time. 
Each time I got a couple of alerts then it stopped. 
I have added both now and have still had a couple of alerts but nothing like the number I was getting. 
ill monitor and see how it goes. 
 

FYI I didn't use the button reset just deleted from the network which deco says is the same as a factory reset. 
Thanks for your rwaponse
 

  @David-TP 

hi

i am still getting device connection emails 

nothing has really changed tbh. 
The deluge of alerts from the other day was due to an issue with the firmware on x50 and the guest network which I use for my IoT devices. These kept on disconnecting and reconnecting. A new firmware was issued that largely fixed this issue although I still get a few network disconnections on the guest network. 

But the fact remains that I cannot stop the email alerts for any device connecting to the network. 
e.g.  if I disconnect my phone from the network then reconnect I get a new decive alert. 
 
Any further suggestions please?