Email problems

We have an Aspire one that my wife uses solely for internet and recently we have had to do a complete re-boot using a usb recovery disc and we are now connected to the internet again!!
HOWEVER....... her email address is [email protected]
I've tried entering this into the email part of the communications suite and it says server is not recognised.
The upshot is she can receive emails but can't send them, she can't even type text in the 'message' part of the email she wants to send (only the address part and the subject part appear to work.
Is this because the hotmail server (and yahoo) are to large for this system? If so is there an easy solution please?
The machine is still in its factory state except I have run the 'updates' - I do not think Mozilla firefox has been updated or amended.