Showing Content for | Change your ZIP Code

Enter another ZIP to see info from a different area. X | `>`

!We can't find that ZIP Code. Try again.

AT&T Postmaster FAQs

This information is intended for ISPs, email providers, customers, and other service providers who want information about the AT&T email service, how it works, and how to resolve related issues.


Frequently asked questions

How do I unblock email messages?

It is never the intention of the AT&T Postmaster staff to block legitimate mail. Unfortunately, legitimate messages are sometimes blocked as a result of our antispam and antivirus measures. We would like to fix these problems as soon as possible, but we need your help. Please email our block list group for more information or to find out how to unblock emails.

Are there any guidelines or standards for sending mail to AT&T customers?

AT&T guidelines and standards for email can be found in our Acceptable Use Policy. AT&T requires that all email comply with the U.S Can Spam Act. Failure to adhere to the AT&T email standards will result in your message being blocked from entering the AT&T network.

What is the maximum size of an email message that an AT&T customer can receive?

The maximum size of an email message that an AT&T customer can receive is based on the individual customer's service type.

Note: Message size includes the combined total of the message text and any message headers and attachments. (An attachment might double in size when it is coded for email.) The available space in the customer's mailbox may also determine if the message is received, regardless of the maximum message size.

Can I request a customer's personal information from AT&T?

Releasing personal and confidential information is against the AT&T Privacy Policy.

My email doesn't appear to have gotten through, but I didn't get an error message back. What should I do?

There are various factors that may cause an email not to be delivered. First, try to send the message to your own email account. If this is unsuccessful, please consider the following:
  • Confirm the email address with your recipient. Check for correct spelling, and if there appears to be a space in the address, make sure that this space should not be an underscore (_). Example: may appear as, causing the underscore to look like a space. 
  • Try to resend the message. Temporary problems between mail servers can sometimes affect mail delivery.
  • If these suggestions do not resolve the problem, please contact your ISP for assistance. There may be a problem with the configuration of your mail client, or your ISP may be experiencing problems with their mail servers.

How do I keep my mail from going to the recipient's Spam folder?

If you stick to the AT&T Acceptable Use Policy, your email will most likely be delivered successfully to the customer's Inbox. If your email meets the guidelines but is still being filtered as spam, ask the AT&T customer to make sure their MailGuard is set to "Review" to allow spam messages to be delivered to a separate MailGuard folder for review. If MailGuard is set to Review and the problem persists, ask the recipient to forward the undeliverable email message to (without the spaces). This will ensure that your message is delivered and not identified as spam.

I sent an email to an AT&T customer but received an error. What does this mean?

There are several reasons why an email may not to be delivered. In each case, the sender will receive an error message that provides more information about why the message was not delivered. Worried your email may have been blocked? Email our block list group for more information or to find out how to unblock emails.

Where can I find information on DKIM?

Information on the digital (DKIM) signatures added to outbound emails sent by AT&T customers is located on the DKIM Servers page of the AT&T Postmaster website.

Most of our customers' accounts are hosted on the Yahoo! system.

See technical information about Yahoo!