Murano

OK, one day my Microsoft outlook works fine the next day Outlook 2003 will allow me to receive emails only but will not allow me to reply on send an email from Outlok 2003. I have verified with my ISP that all the setting are correct. There is not error message. ISP tell me there is an issue with the outlook software. When I reply the out going email just sits in the out box trying to send. I am using Sympatico. Has anyone had a similar expereince or know how to work around or correct this. It is very frustrating. Thanks