this has been driving me NUTS!!!

lately..any time i go to send an email....i get an error message that some 
of the tasks could not be performed....and am instructed to look at the 
details.

well..there is nothing in the details dialogue box!

the email DOES go thru...but it languishes in my outbox and never hits my 
sent box and i have to delete it or save it.

any ideas?