This suggests that Outlook Express has lost the settings for the outgoing mail server.
Go to the website of your grandad's e-mail provider. (That's probably his ISP, but not necessarily)..
Search through the help pages to find the POP3 server information. (It will probably be something like 'pop.ispname.com').
Open Outlook Express. Follow this path:
Tools > Accounts > Mail > (Click on the account name to highlight it) > Properties > Servers > (Enter the POP3 information into the appropriate field) > Apply > OK > Close.
Hopefully, that will fix the problem. If not, please post again.
Chris