Enhance the email sending feature so that different types of email can be sent from different addresses

[simon-20]

Brief Description
Currently all emails are sent with the same From: address, support@iatistandard.org. But this means that the notification of new organisation emails, which are also sent to that address, because they are for the Secretariat Support team, are rejected by Zendesk (which handles support@).

So we need to allow for different From: addresses.

I've created code@ as a valid sending address on Azure. So need to modify the code to allow a different from for that.