SMTP ERROR: Password command failed - by: glyridis

Hello everybody!

I'm trying to send e-mail to user and get the following ERROR:

2016-11-29 10:50:35.052 ..... SCRIPT .... ::1 /projeqtor/tool/sendMail.php
2016-11-29 10:50:35.061 ..... SCRIPT .... ::1 Page=sendMail.php
2016-11-29 10:50:35.113 ..... SCRIPT .... ::1 ->/tool/sendMail.php
2016-11-29 10:50:35.128 ..... SCRIPT .... ::1 sendMail_phpmailer
2016-11-29 10:50:36.724 ***** ERROR ***** Error sending mail
2016-11-29 10:50:36.724 ***** ERROR ***** SMTP Server : tls://hera.gsis.gr
2016-11-29 10:50:36.725 ***** ERROR ***** SMTP Port : 587
2016-11-29 10:50:36.725 ***** ERROR ***** Mail stored in Database : #6
2016-11-29 10:50:36.726 ***** ERROR ***** PHPMail error : SMTP connect() failed. github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
2016-11-29 10:50:36.726 ***** ERROR ***** PHPMail debug : 2016-11-29 09:50:35 CLIENT -> SERVER: EHLO localhost
2016-11-29 09:50:35 CLIENT -> SERVER: STARTTLS
2016-11-29 09:50:35 CLIENT -> SERVER: EHLO localhost
2016-11-29 09:50:35 CLIENT -> SERVER: AUTH LOGIN
2016-11-29 09:50:35 CLIENT -> SERVER: Zy5seXJpZGlzQGdzaXM=
2016-11-29 09:50:35 CLIENT -> SERVER: R0wyMTAzNjghIQ==
2016-11-29 09:50:36 SMTP ERROR: Password command failed: 535 5.7.8 Error: authentication failed: UGFzc3dvcmQ6
2016-11-29 09:50:36 SMTP Error: Could not authenticate.
2016-11-29 09:50:36 CLIENT -> SERVER: QUIT
2016-11-29 09:50:36 SMTP connect() failed. github.com/PHPMailer/PHPMailer/wiki/Troubleshooting

2016-11-29 10:50:45.048 ..... SCRIPT .... ::1 /projeqtor/view/admin.php

my settings in global parameters are as per attached screenshot

Please, can anybody give me a hint??

Thanks in advance