ZImbra Desktop fails to send email from my yahoo account
I have added my yahoo account on my zimbra desktop and this worked well for the past few 4 months.
I now am getting the error "SendMessage request failed: Blocked for security reasons." everytime I send an email from my zimbra desktop yahoo account.
Sending emails from all other accounts on my zimbra desktop works well.
I deleted and re-added this account and the error persists.
I have tried sending mail from my yahoo webmail account and this works fine.
I have searched google for this error and the zimbra forums but no one has received this error before.
Please advise as to what the problem can be.