Form Email Errors on Comma delimited list

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Hello,
I created a contact form and have been using it for a while. I have added multiple emails in a comma delimited list. Now for some reason the emails will not go to multiple emails. I just get "Mail Exception Occurred. Unable to send mail: Unable to send mail: mail() [function.mail]: Bad parameters to mail() function, mail not sent."

ex of emails: "email@email.com, email2@email.com"

If I just put one email address it seems to be fine though.

I have been searching for an answer but everything I have found says that this issue should be fixed.