Help ...below is the message I receive when I attempt to send out email from live mail.  Incoming works perfectly.   I contacted the company Windstream that does my email and they claim the problem is with live mail.  It appears that all my settings are correct and this problem is not a windows 10 problem since it also occurred with windows 7 prior to my update to 10.   I have changed the port numbers twice on Windstreams suggestion from 25 to 587 and that does not fix.   Windstream claims if I go to their website I will be able to send emails there.   My question is why can I send gmail with no problem and why does this email not send.

Any advice would be much appreciated.

An unknown error has occurred.

Subject 'Test'
Server Error: 421
Server Response: 421 pacmmta54.windstream.net pacmmta54 4.7.1 - Connection Refused - 72.23.197.161 - Too many connections
Server: 'smtp.windstream.net'
Windows Live Mail Error ID: 0x800CCC67
Protocol: SMTP
Port: 587
Secure(SSL): No