thats probably it, just added avast...will check if i have it marked

<P>This is the error message I am getting when I send out emails now.</P> <P mce_keep="true"> </P><FONT size=2> <P align=left>Delivery has failed on the enclosed message for the following</P> <P align=left>reasons reported either by the mail delivery system on the mail</P> <P align=left>relay host or by the local TCP/IP transport module:</P> <P align=left mce_keep="true"> </P> <P align=left>550 Valid Auth required to continue.</P> <P align=left mce_keep="true"> </P> <P align=left mce_keep="true"> </P> <P align=left>We recently changed service providers, but that ha snot mattered in the past.  Could this be an issue?</P></FONT>

<p>Service providers have been known to change their authentication requirements for relaying mail (like changing the TCP/IP port).  Obtain the current authentication requirements from your service provider for sending mail then check the settings of your configured SMTP host.</p><p> </p>

Are you using Avast free antivirus - If you have the scan outgoing emails box ticked it won't send emails (at least on my systems)