Hi Rob,
This issue not related the file permissions. To prevent spamming from our servers, we have made a few changes to the sendmail() and now allow mails to be send out only using SMTP authentication. In case, even after using SMTP authentication method, the issue persist, we suggest you to send us an email with the screen shots of the email settings which you are using in your application at
support@limedomains.com. We will investigate and provide you a resolution at the earliest.
Thanks & Regards,