Subscribe by Email not sending Posts to Email list

I noticed just yesterday that my daily posts are not being sent to my mailing list. I also checked the Email log to see it it was just delayed but could not find any listing of email logs for yesterday or for previous days. I have been using this plugin for our subscribers mailing list for over 3 months now with no issues.
I posted another post today and have noticed that it was not sent out also. I would appreciate if you could help resolve issue. I believe It began between Saturday and yesterday as the posts were sent out Friday.
Thank you.