This is just to save someone a headache down the road. Our form submission notification emails were to be sent to 4 addresses and none were arriving. If I limited it to just one email address, the notification email arrived fine. I checked the logs and it said it could not deliver due to a syntax error. Turns out instead of using the common practice of having a space after the comma like this...
email1@company.com, email2@company.com
you have to remove the space to avoid the error...
email1@company.com,email2@company.com

So when it says...
Notify me by email when people submit this form
(Seperate multiple emails with a comma)

It really does mean JUST a comma. Hope this saves someone some time and headache.
Cheers,
C

(oh, and 'seperate' is spelled wrong)