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Undeliverable E-Mail


Undeliverable E-Mail

Very recently i've gotten back as undeliverable e-mails sent to "Hotmail" and "MSN" -service provider was mentioned as cause.
Message 1 of 6

Re: Undeliverable E-Mail

hi hankoc!

try to check first with the HotMail/MSN recipient(s). make sure that your AT&T email ID is not listed under their Spam/Blocked addresses feature.

if not listed, most probably HotMail and MSN are both automatically blocking/rejecting the AT&T's domain. it could be for security reasons. lately, there have been lots of phishing/spam mails originating (or pretending to be) from AT&T domains. Hotmail and other email providers can ban AT&T domains once they received tons of reports of these possible spam abuse.

for more info:
Why an I receiving email errors like "Service Unavailable" and "Your Domain Is Banned"?
Message 2 of 6

Re: Undeliverable E-Mail

Thanks much!-Hank
Message 3 of 6

Re: Undeliverable E-Mail

BTW, are you getting any specific error code? if so, see if it may be listed below.

Error Code 421-failure in DNS look-up.
Explanation: There seems to be a failure in your IP reverse DNS lookup. Your IP address must have a valid reverse DNS entry to send mail to the AT&T domain. Please correct the error or contact your service provider for assistance before trying again.
What to do: The system administrator should consult

Error Code 450 busy--Please try again later
Explanation: The sending system has requested more resources than are available at the moment.
What to do: The sending system should re-try.

Error Code 521 < > is blocked
Explanation: The sending system has been identified as a source of spam.
What to do: Please see for more infomation.

Error Code 550 [suspend] Mailbox currently suspended--Please contact correspondent directly.
Explanation: The account of the BellSouth customer is suspended.
What to do: Contact the customer directly.

Error Code 550 [permfail] requires valid sender domain
Explanation: We were unable to verify the identity of the sending system.
What to do: Administrator of sending system should enter correct information in DNS (domain name system)

Error Code 550 unauthorized interface for < >
Explanation: The sending system is not recognized as a valid source of e-mail.
What to do: Correspondents should use registered mail systems provided by a major ISP or hosting service.

Error Code 550 < > blocked by ldap: ou=rblmx, dc=bellsouth, dc=net
Explanation: The sending system exhibited behavior associated with spammers and was blocked.
What to do: After taking steps to mitigate their spam or virus problems, the adminstrators of affected systems can send unblock requests from

hope this helps! :smileyhappy:
Message 4 of 6

All and emails being blocked by hotmail/msn - please help!

Thousands of hotmail users (and att/ senders) of email are being impacted. Can you and msnlive support please work together to solve this? Everyone is getting some variation of the following message: 550 REPLY: 550_SC-004_Mail_rejected_by_Windows_Live_Hotmail_for_policy_reasons._A_block_has _been_placed_against_your_IP_address_because_we_have_received_complaints_concern ing_mail_coming_from_that_IP_address._If_you_are_not_an_email/network_admin_plea se_contact_your_ Please post an explanation in system status or make a mailing to all ids on Let us know that you are aware of the problem and give an expected resolution date. Real people and their businesses are hurting.
Message 5 of 6

Re: All and emails being blocked by hotmail/msn - please help!

If you are using a PC/MAC email application, check how you are sending your email.

I used to use the old pop/smtp servers of ""

But, there are new ones: I switched to "" and "". There are new ports (995 and 465) and you have to ensure that authentication is occurring. You can find the specifics for your email application on your provider's web site.

What I think was happening (just a uneducated guess,) is that by using the old servers, our emails were not being authenticated correctly and were therefore being flagged as spam. When I used the old server, that IP address was in the spamhaus IP list. It should be there, but unless your email is 'authenticated' it will be flagged as spam. I learned a lot reading on

Message 6 of 6
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