Many people are having issues with their Mozilla Thunderbird email client not being able to send emails through their ATT/Yahoo account. I was having this same problem, however a support ticket to ATT/Yahoo gave me a solution which I am posting here for others to try. This solution is working for me. Here is the support email I received:
If you are using a mail client and the error you get shows an Error 553, then we need to verify your third party e-mail address. I checked our Network Bulletin and found an outage with event number 1xxxxxx stating that due to a security patch upgrade some AT&T Yahoo! Customers may receive error 553 address not verified when sending email.
Mr. X, just recently AT&T Yahoo! implemented a security fix to improve our e-mail servers’ security. Up until then, AT&T Yahoo! members have been able to configure an external e-mail client with a [From] e-mail address that is not associated with their AT&T Yahoo! Mail account. The security fix I mentioned is designed to remove this capability. This security fix will affect members that have a non-verified e-mail address that is not associated with their AT&T Yahoo! Account.
You are receiving Error 553 because your [From] email address is not verified. Per Yahoo, verification is required of a valid, alternate e-mail address to protect your Yahoo! account and to:
a. Communicate with you if you’re unable to login to your account
b. Alert you if we should witness suspicious activity with your account
c. Issue you a new password if you ever forget your current one
d. Ensure that your email address is valid and owned by you.
To verify your [From] e-mail address, and thus, to have this error fixed, kindly follow the instructions below:
1. Sign into the AT&T Yahoo! Web Mail through the website:
http://att.yahoo.com/mail
Please enter your complete e-mail address (e.g. username@sbcglobal.net) and password to sign in.
2. Click the [Options] link on top.
3. Click [Mail Addresses] under the [Management] section.
4. Click the [Add] button.
5. In the box, enter an account name for your own reference (for example, Work, School, etc. ? no one else will see this) and click [Continue].
6. In the first one, put the name that you would like others to see when they get e-mail from this address. In the second field, type the external e-mail address that you would like to display in the [From:] email address.
Note: You will be asked to verify this other address in an e-mail we will send to you there.
7. Click [Continue].
8. Click [Skip this Step].
9. On the page that opens, check to make sure you have entered the correct e-mail address. If you need to make any changes, click the [Edit Address] link. If everything looks correct, click [Send Verification] to generate the email we send to you to make sure this is an actual account you use. We need to do this to help prevent spam.
10. The [Verify Account] page opens. To complete your setup and start sending mail from the new address, please follow the steps below:
a. Leave this [Verify Account] page open.
b. In a different browser window or application, sign into your alternate e-mail account, the one that you want to use as a [From:] address.
Note: if you will be using another Yahoo! Account, you can open it through another browser such as Internet Explorer, Mozilla Firefox or Netscape.
c. Look for an e-mail from Yahoo! Member Services, and open it.
d. Copy the [confirmation code] in the last line of the e-mail by either double-clicking it to highlight the code in blue, and then click the [Edit] menu and select [Copy].
e. Get back to the [Verify Account] page and paste that confirmation code in the box beside [Confirmation Code:]. You can paste by clicking [Edit] and selecting [Paste].
f. At the bottom of the page, click [Verify Account].
g. A sign-in page opens with your ID already filled in. Enter your password.
h. You will now see the verified e-mail account in the list on the [Mail Accounts] page.
You can now configure this e-mail address on Thunderbird.
Finally, I would like to provide you with the list of e-mail addresses that can be used as a [From] address:
1. Verified e-mail address.
2. Extra E-mail Address. For more information, please refer to the website:
http://help.yahoo.com/l/us/yahoo/mail/original/tools/index.html
3. Address Guard or Disposable E-mail Address. For more information, please refer to the website:
http://help.yahoo.com/l/us/yahoo/mail/original/mailplus/addressguard/index.html
After following the steps above, please try to update your mail settings. For your reference, let me give you the settings for your mail client:
Incoming (POP3) server: pop.att.yahoo.com
Outgoing (SMTP) server: smtp.att.yahoo.com
Username: blahxxxblah@sbcglobal.net
Password: your password
Incoming mail server: POP3
Outgoing mail server: Outgoing server (SMTP) requires authentication should be checked
Incoming mail port #: 995, secure connection (SSL) checked
Outgoing mail port #: 465, secure connection (SSL) checked
In line with this, please try to remove then recreate your e-mail settings. For your reference, here are the steps below:
Important: Please note that you have to select the checkbox for [This server requires a secure connection (SSL)] first before you change the port numbers on your e-mail client, otherwise, the settings would not take effect.
1. Launch your Thunderbird program.
2. Click on [Tools] and go to [Account Settings]
3. Click on [Server Settings] on the left pane.
4. Please make sure that [pop.att.yahoo.com] is typed in on the [Server Name] box and type in [995] for the [Port] box.
5. Under [Security Settings] section, please select [SSL] and check [Use secure authentication].
6. On the [User Name] box, type in your complete e-mail address (ex. blahxxxblah@sbcglobal.net)
7. Click on [Outgoing Server SMTP] on the left pane.
8. Highlight your AT&T outgoing server and click on the [Edit] button.
9. Make sure that the [Server Name] should be [smtp.att.yahoo.com] and the port number is [465].
10. Under [Security and Authentication], check [Use name and password].
11. On the [User Name] box, type in your complete e-mail addresses (ex. blahxxxblah@sbcglobal.net) and your password on the [Password] box.
12. Under [Use Secure Connection] section, select [SSL].
13. Click on [OK] to close the SMTP advance settings.
14. Click on [OK].
After doing the above steps, please restart your computer to refresh the settings. We could test the account if it is working by sending out a test mail on our Test Servers. Please create a new message and send it to [autorsvp @ sbcglobal.net]. You will receive a confirmation reply if the message has been successfully sent. You can also try sending out a test mail to your own e-mail address to check if you will be able to receive the message.
Unfortunately, configuring the settings of your Thunderbird e-mail client is currently beyond our scope of support since we do not have the knowledge base about the program. Technical support and troubleshooting is available by contacting AT&T Support + or Mozilla, the Original Software Manufacturer (OSM).
It has been my pleasure helping you today, Mr. X. Thank you for choosing AT&T Internet Services.
Have a nice day!
I can’t promise that this works for everyone, but it has worked for me.
