How to configure SMTP settings to get email notifications in Integrity lifecycle manager with sendgr

We have PTC ILM 12 version and we are using ldap authentication.

When we tried to enable SMTP for ILM, its not working

1) Admin client -> enabled mail server 

2)Admin client -> configured notifier mail address

3) created notification rule for my usre id and its not sending.. getting  error as 'unauthenticated senders are not allowed"

Note: tested sendgrid functionality over command line from server with the same notifier usrer mail addrss.