I did some googling and found the following about GoDaddy:
1/ The "From:" email address CANNOT be a gmail, yahoo, hotmail, aol, msn etc email address - if it is then the email will get dropped as spam.
2/ The "From:" email address is best set up as an address on the same domain as your site - so if your blog is http://www.example.com you need an address firstname.lastname@example.org
3/ The "email@example.com" email address given in the example above MUST actually exist on your domain. You may need to create this email.
4/ You can only send to 250 (for shared hosting) or 1,000 (for dedicate or VPS) different email addresses in 24 hours, any more unique addresses than that will be blocked.
5/ PHP mail() function is totally unsupported on Windows IIS hosting, you must be on Linux.
6/ It may be worth channeling your emails via the relay-hosting.secureserver.net server using something like the SMTP Mailer plugin.
Also consider that the Digest email will only send posts made since the last digest was sent and if you've only just set it now it will collect posts made between now and when you've scheduled it to run -it does not schedule for now and look backwards.