Cant send email

Have not been able to send or receive email since Wed. Talked to verizon,
they stated they knew of the issue and were working on it. Yesterday i was
able to receive email but not send, now today, still the same, I receive it
but can't send it, yesterday the automated message at verizon was still the
same, that they knew of the issue and were working on it, so now I'm coming
to all of you, I copy and pasted the error below...what's up?

The message could not be sent. The authentication setting might not be
correct for your outgoing e-mail [SMTP] server. For help solving this
problem, go to Help, search for "Troubleshoot Windows Mail", and read the
"I'm having problems sending e-mail" section. If you need help determining
the proper server settings, please contact your e-mail service provider.

The rejected e-mail address was 'melissaschneckplbg@xxxxxxxxxxx'. Subject
'Re: Re:', Account: '', Server: '',
Protocol: SMTP, Server Response: '550 5.7.1 Authentication is required to
send mail as <vzetfna1@xxxxxxxxxxx>', Port: 587, Secure(SSL): No, Server
Error: 550, Error Number: 0x800CCC78