Please help - I've been trying to set up my Hotmail account with Windows Live Mail for the past few hours and keep encountering problems. I am now able to receive emails, but not send them. I have Windows 10. The error message that comes up is shown below:

An unknown error has occurred.

Subject 'Nowy adres e-mail'
Server Error: 550
Server Response: 550 5.3.4 554-554 5.2.0 STOREDRV.Deliver; delivery result banner
Server: 'smtp.live.com'
Windows Live Mail Error ID: 0x800CCC69
Protocol: SMTP
Port: 587
Secure(SSL): Yes

Any suggestions would be greatly appreciated!