Thanks for the pointers. Looks like the problem is not with the site but my domain email (same as site url) which I will probably have to take up with my provider. I changed the email account from the email I use for the site to my personnel email and its working fine. Spam filters were turned off for the test so it wasn't a filtering issue with that. Basically the email addresses that match the site domain aren't going through.
ex.
phil@XXXXXX.org or admin@xxxxx.org get lost system says it sent them but they never arrive