I am tired of reading post after post searching for the message I receive.  

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Windows Live Mail v. 16.4.3528

I have "repaired" using the control panel, add/remove programs.  I have uninstalled using CCleaner, then installed just the mail part and the whole set of Windows Live Essentials.  I uninstalled using add/remove programs.

I created a second account on my pc, used Windows Live Mail in that account with no problem.

This problem began two days ago without provocation: as in, I did not update or add anything to the pc.

Any attempt to send a message results in "The message could not be sent.  Some of the recipients for this message are not valid.  Please verify the names."  This even though the name is correctly entered.  If I choose "To..." in order to choose a recipient an error is returned, "Unable to choose recipients".  

By the way, the choices in "Topic" don't cover inability to open or send emails.