emails not being sent

I am getting an error message which reads Error: too many errors which is a Norton error message. I am able to send emails sporadically, this morning I sent 4 and all others I sent afterwards received this error message. When the message comes up the email goes into the sent mail, but it is not ever received by the recipient. Its almost as if I have reached the capacity of sending emails and for a while I cannot get any to go through... Later I may try these emails again and they will go through successfully.... IT IS VERY ANNOYING. Can anyone help?