I have been successfully using WebMail for my verizon.net email account for years.  All of a sudden, I cannot send emails, but can receive.  Another (perhaps) related problem is that I keep receiving "unable to deliver" notices for addresses to whom I have never sent an email--all these addresses appear to be foreign, mostly from Germany.  The error message I get when attempting to send is:

An unknown error has occurred.

Subject 'Fw: ShareFile Activity Notification'
Server Error: 554
Server Response: 554 5.7.1 The message you attempted to send was determined to be spam. Please visit http://www.verizon.net/spamfaq for more information.
Server: 'smtp.verizon.net'
Windows Live Mail Error ID: 0x800CCC6F
Protocol: SMTP
Port: 465
Secure(SSL): Yes