Need help on using webhooks in notifications


I am trying to send alerts into WebexTeams using webhooks. I have one webhook url (by using it with curl command i am able to send messages into WebexTeams room ). but, while i am giving this url inside a webhook notification channel and doing Send Test, showing error Failed to send alert notifications.
i am using grafana 5.2.4 version.
I am thinking is there any thing to configure/add in the grafana.ini file for using webhooks
team, Can you help on this?