The AT&T Yahoo Business Email SMTP server requires authentication. To learn how to configure your email client, please choose from the following programs:
If your program and version are not listed above, you may have trouble connecting to the Yahoo Mail SMTP servers. Yahoo does not support other programs and versions.
Please make sure that you have entered your AT&T Yahoo Business Email address as the "From" address in your email client. You will not be able to send mail if you have entered another address.
Note that Yahoo limits messages sent via SMTP to 500 per day, and each message can be sent to only 100 recipients at once. If you're trying to send an email to more than 100 recipients, you will see an error telling you that some of your contacts did not receive the message. Please try resending your message but limiting your recipient list to 100 or fewer.
Important note: If you have tried the above steps and continue to have problems sending mail, your Internet service provider (ISP) may not allow its users to send messages with other companies' SMTP outgoing mail servers. If you have set the "Outgoing Mail (SMTP) Server" field in AT&T Yahoo Business Email to smtp.bizmail.yahoo.com, have set your client to use authenticated SMTP, and find that you can receive but cannot send messages, you may have to use your ISP's SMTP server address rather than Yahoo's. Learn more.
If you're unable to send email, try using port 587 when sending via Yahoo's SMTP server. Here's how to make this change: