Adding IP as outbound to whitelist secure external host

Question

First of all I am a newbee in Azure.

 

My client have procured an Azure subscription, where I have a app service which runs in .Net core application.

 

I have to connect to a secure location from a WebJob, I can see it's failing. Even I am not able to connect with SMTP server to send mail from that WebJob of the app service.

 

My question is if such type of configuration exists in Azure, where I have to add the host IP address to whitelist those.