Why you may receive a delivery failure message when sending email messages to Yahoo! from an third-party service.

When you see this error message in your SMTP logs (where x.x.x.x is your IP address), it’s because of either of the following:

• We are seeing unusual traffic from your IP address.
• Email from your mail server is generating complaints from Yahoo! Mail users.

Note: This is typically a temporary situation and we encourage you to retry sending email to our servers approximately four hours after you encounter this error.

If you see this error consistently over a 48-hour period, and you are the administrator for the message content or mailing policies, we ask that you review outgoing messages for potentially objectionable content or practices.

Please know that Yahoo! is unable to disclose specific information regarding our filtering practices; however, you may find it helpful we review our best practices for bulk senders.

If you are not the administrator of the mail server in question, please contact the administrator directly with the error message you are receiving.