Yahoo has been blocking delivery of email messages originating from Middlebury College for the past two days. They now report that they have modified their settings so more messages should pass through. They provide this additional information:
Please be aware that Yahoo! Mail users are able to set their own preferences for the manner in which they receive your mailings. If the recipients of your messages want to ensure they receive your emails in their Inbox, you may want to ask them to set up a filter in Yahoo! Mail specifically for your emails, or have them add your email address(es) to their Yahoo! Address Book.
Please refer to the Yahoo Help page for more information on Yahoo's recommended best practices for sending mail from any mail server to Yahoo! Mail users.