If a "Relaying Not Allowed" error appears when you try to send email from a POP email client, your ISP (Internet Service Provider) is not permitting an outside SMTP server to send email. Because of this, you may need to use your ISP's outgoing mail server (SMTP) setting.
First verify that the following settings are correct in your email client (your email client is the desktop application used to check your email, such as Outlook or Eudora):
If these solutions don't work, you may need to use your ISP's outgoing mail server (SMTP) setting. Contact your ISP for the appropriate SMTP setting for sending mail. (Using your ISP's SMTP server should not affect the functionality of your Yahoo! Domains email account.)