Autoresponder not sending any messages?

Greetings everyone I'm having trouble getting my autoresponder to send out any msgs.? I'm using Interspire eMail Marketer and the install went smoothly. Cron jobs is running smoothly as well. The only hitch is that none of the messages are going out, even though I get system messages saying that the message has been sent successfully.:confused Has anyone else encountered this problem? It seems like a simple overlooked solution... Oh and I contacted my hosting support team and they said it was due possibly to heavy server traffic? Huh!