Email stopped working

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?

In the Mail menu at the upper left, choose Preferences. Look through that for any clues about this port 25. If there is a reset to defaults, try that.

Mail users, help!

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.

is your SMTP server the same as your internet provider? Many, if not most, ISP's block 25 traffic to SMTP hosts other than their own.

Also are you using a full address? Such as [email protected]

because "Larry Mark" is not a valid email address

I should have been more clear. Larry Mark is the name in the address book that has my correct email address ([email protected]). When clicking the name in the address book and "to" it should have the correct email address. When sending an email it adds Larry to the email address which causes the error. There is no name that is just Larry in the address book. I don't know why Larry is added to every email address and how to stop it.

Sounds like some corrupted metadata somewhere. Possibly in ~/Library/Application\ Support/Addressbook/

that being said, the only way I know to deal with anything in there is to move it.. which removes the addressbook entries in their entirety.