Yes, this is the debug log of the test with Easy WP Smtp plugin:
CLIENT -> SERVER: EHLO http://www.mywebsite.it
CLIENT -> SERVER: AUTH LOGIN
CLIENT -> SERVER: bmV3c2xldHRlckB0ZWF0cm9jcmVzdC5pdA==
CLIENT -> SERVER: dmlhZGVsZWRkYQ==
SMTP ERROR: Password command failed: 535 5.7.0 …authentication rejected
SMTP Error: Could not authenticate.CLIENT -> SERVER: QUIT
SMTP Error: Could not authenticate.
How come? NL plugin worked fine, since last week.