I'm helping my mother who has an old mac laptop. I'm not familiar with macs so please bear with me. Her email has stopped working. She's using OS 10.3.9. It's apple's email app. I notice that when trying to send it sometimes says that it timed out on port 25. She seems to receive items but can't send. She's sent things to me which haven't gotten through. She used to have a percentage bar and a sound when mail was sent which has stopped. She has full bars for her wireless connection and safari browses the internet fine. What should I be looking for?

Perhaps her ISP changed their mail server addresses.

I changed the port to 587 which seems to have helped a little. After seeing the percentage bar an error message occurs " delivery failed due to illegal address Larry". I received several test messages at my end even with the error message so they were sent. If the address is typed in rather than through the address book the error appears right away and I don't think that message got sent. There is no address for Larry in the address book but there is for "Larry Mark" that has my correct email address. I tried deleting and recreating "Larry Mark" several times but the error still occurs.