wso2esb - How correctly make sequence for WSO2 API? It's breaking email send -

i create simple api uri-template /my_context/{param1}?b={param2}

i created simple sequence sending email message endpoint address

mailto:user@gmail.com 

i opened link

/api/my_context/123?b=222 

and found in log messages:

send to: user@gmail.com/my_context/123?b=222 incorrect address. 

why wso2 esb append uri email address?

removing rest_url_postfix property change behavior.

<property name="rest_url_postfix"  action="remove" scope="axis2"/>