On each channel we have a field to enter an email address to get a notification, only one email can be used here.
To forward to multiple email addresses you will need to forward the email from your email service or use a 3rd party service instead.
How to forward in Gmail:
How to add forwarding address in Gmail: https://www.lifewire.com/how-to-forward-your-gmail-email-to-another-email-address-1171906
How to use filters to forward an email: https://www.lifewire.com/how-to-forward-gmail-email-using-filters-1171934
Use a 3rd party tool
You can open a paid account here: https://forwardemail.net/en
You can create a special email address to enter into Channex and then set that up to forward to 1 or many email addresses in your side.
Step 1: Create a Paid Account with Forward Email
You will have a choice of domains:
Choose one of their domains and press continue
Step 2: Add Alias
Click on Generate Random Address or create your own text
Check the box for IIMAP/POP3/CalDAV (optional)
Step 3: Add forwarding email addresses
Add your emails with a comma to separate them
Add a description if you want
Check the box to activate
If you have no paid account you can enter payment details to subscribe