Windows Mail Not Sending

[Wen]

I have not been able send any email in a few days.
I have emails ready to send however nothing happens.
There is an email there which when you click on it, the email says

Message could not be displayed
Windows Mail encountered an unexpected problem while displaying this
message. Check your computer for low memory or low disk space and try again.

I have almost full memory as everything is stored on an external drive. I
can't delete the msg cause when I try this error comes up;
" An unknown error has occured.

What should I do?

 

[Wen]

I HAVE FOUND THE UPDATE IN A EARLIER POST.
THANK YOU FRO TAKING THE TIME TO READ THOUGH