This article describes how to send SMTP-authenticated email to Yahoo! Groups and avoid a delivery failure citing a “suspected guidelines violation”.  By requiring proper authenticationExample of proper authentication: Using a yahoo.com address with the correct yahoo.com SMTP server address. 
Example of improper authentication: Using a yahoo.com "From" address with a non-Yahoo! SMTP server., this greatly reduces the amount of spam delivered to Yahoo! Groups.

Your email will need to be authenticated by the email server (SMTP) affiliated with your posting (or “From”) address. If you use any of the following methods to send email, you may need to update your SMTP settings:

• Using an external email application (such as Windows Live Mail, Microsoft Outlook, Mozilla Thunderbird, Incredimail, Eudora, and others)
• Sending email from an  alternate webmail service For example: Sending email using Yahoo! Mail but using a non-Yahoo! “From” address.
• Using a bulk-mailer application, browser add-on, or automated/scheduled web service to post messages

Using a Yahoo! Mail address

If your Yahoo! Mail account is POP/SMTP-enabled

Please review the article relevant to your email set up below:

• Using Yahoo! Mail Plus in Windows live Mail

• Using Yahoo! Mail Plus in another external email client

• If you are using an alternate webmail service (using a Yahoo! “From” address), bulk mailer application/service, browser add-on, or automated/scheduled web service to post, use the Outgoing mail server (SMTP) settings listed in this article.

  • Not all of these services and applications may offer SMTP server authentication.  If your service/application does not offer SMTP authentication, you may need to use a different method to send email to Yahoo! Groups.

Note: The above instructions apply to Yahoo! Mail in the US. SMTP server names may vary depending on your location.  If your account was registered outside the US, please visit Yahoo! Mail Help for assistance with SMTP server authentication.

If your account is not POP/SMTP-enabled

• You can subscribe to Yahoo! Mail Plus to gain access to our SMTP server. 
• If Yahoo! Mail Plus is not for you, feel free to use Yahoo! Mail via the web to send messages. Webmail messages are authenticated by the Yahoo! Mail servers. Alternatively, try registering an email address associated with your existing SMTP server and add it as a alternate posting address in Yahoo! Groups.

Using a Gmail address

• Using Gmail in an external email client
  • Note: This link points to a Gmail resource and is not maintained by Yahoo!. For assistance with these instructions, please refer to Gmail’s support resources.

Using another email provider’s email address

• Your email provider should be able to offer information on their outgoing email (SMTP) server. Please refer to their support or help pages for assistance with server addresses and other settings with your email configuration. 

If you’ve tried the above solutions and emails to Yahoo! Groups still result in a “suspected guidelines violation”

If you have the option, try re-sending the same exact message through  the webmail service affiliated with your email addressFor example: Visit http://mail.yahoo.com if you have a Yahoo! address. Webmail messages should always be properly authenticated and deliverable as long as they do not contain “spammy” content. If you receive the same delivery failure notification, our spam filters may have detected a “false-positive” message. Occasionally in our efforts to make Yahoo! Groups a more secure and spam-free service, we may incorrectly classify some mails as spam. We regret every such instance. 

If you sent an email to a group and received the delivery failure message due to a possible spam-filtering error, please contact our Customer Care team.

Some ISPs may restrict access to non-ISP SMTP servers. If your ISP enforces such restrictions, we recommend either using the webmail service affiliated with your email address or adding your ISP’s email address as an alternate posting address in Yahoo! Groups. When using an alternate posting address, make sure your ISP's email address is selected in the "From" field.