NIS blocks sending emails with error 1003,9

I am keep getting this error, started about six weeks ago and I am at my wits end. Both ISP and Norton deny it is anything to do with them. When I send an email, it says it has been sent and then the Norton error screen pops up with email not sent error 1003,9.

 

I am running XP and using outlook 2003. And it keeps happening, although email says its been sent, and the popup form Norton takes a few minutes to come up. So it is not easy to work out which emails were sent and which weren’t. This is crippling my productivity. Please can anyone help?

 

NORTON WHAT IS THE ANSWER PLEASE ???? your “help” desk told me other people had had this problem but declined to explain what the problem was.

 

However I have noticed that the problem occurs when the sender email address is in quotes eg abc@xyz.com

whereas it doesn’t happen if there are no quotes eg abc@xyz.com. Has anyone else noticed this.

What I am doing is every time I reply to an email I re input the sender address. That seems to work, but makes no sense

 I would be very grateful for any help please.

Thanks

 

<<Edit: Included fictitious email address instead of a possibly real ones for examples given in the post>>