Relaying disallowed while sending email via kerio connect using SMTP Server =smtp.zoho.com

Relaying disallowed while sending email via kerio connect using SMTP Server =smtp.zoho.com

Hi, 
I have just bought the 30 users package and now i am in between setting them up here in my company premises

the setup is like that

1 - i've some users account at accounts.zoho.com
2 - i fetch them to here in my company email client (kerio connect) using pop3 (till this all working fine we got every emails from our customers)
3- then i setup SMTP Setting smtp.zoho.com 587   screenshot attached (i also tried 465 as well)  
user a_user@mydomain.com  password (respective pwd  NOTE : i tried every combination of the settings in the attached screen shot but to no avail.

and when my users tried to send email to customers then they received this error message every time 

Your message did not reach some or all of the intended recipients.

 

      Subject:    RE: xyz

      Sent: 18/12/2017 11:43 AM

 

The following recipient(s) cannot be reached:

 

      abc@yahoo.com on 18/12/2017 11:33 AM

            smtp.zoho.com: Failed (553 Relaying disallowed as <someone@mydomain.com>)

 

      def@gmail.com on 18/12/2017 11:33 AM

            smtp.zoho.com: Failed (553 Relaying disallowed as <someone@mydomain.com>)

 

      ghi@hotmail.com on 18/12/2017 11:33 AM

            smtp.zoho.com: Failed (553 Relaying disallowed as <someone@mydomain.com>)


please suggest a solution

thanks