Unable to send email to Yahoo accounts

It appears we are unable to send emails to any Yahoo account, ie, yahoo.com or yahoo.de. Other email providers work just fine Gmail and other corporate addresses.

The emails just sit in queue waiting to send, the only error i can see from Exchange System Manager is "The connection was dropped by the remote host". I have configured rDNS for our domain and it does report back with the correct IP address. I have tested our SMTP and domain using MXToolBox.com and everything is good according to MXToolBox, also, our IPs are not on any black lists for spam.

We are running Exchange 2003 on Server 2003 R2, any help is appreciated.


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Viral RathodConnect With a Mentor ConsultantCommented:
To telnet to yahoo.com first check the IP Address of yahoo.com by running following command

>set q=mx

Non-authoritative answer:
yahoo.com       MX preference = 1, mail exchanger = c.mx.mail.yahoo.com
yahoo.com       MX preference = 1, mail exchanger = d.mx.mail.yahoo.com
c.mx.mail.yahoo.com     internet address =

Then telnet to c.mx.mail.yahoo.com on 25 port
C:\>Telnet c.mx.mail.yahoo.com 25

Send the test mail and letus know the results.
Yahoo may have blocked your domain or IP due to what it has suspected as suspicious SPAM activity in the past.
Tony JLead Technical ArchitectCommented:
Also if it's a new domain or changed IP it can take them up to 48/72 hours before accepting mail.
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mcjim2kAuthor Commented:
If Yahoo has blocked the IP, how do I check and get it unblocked?

This is not a new domain and it appears the issue has been going on for a few weeks.

Thanks for the comments.
Viral RathodConsultantCommented:
Right : May be Yahoo.com have blocked your domain or IP Address

To cross check the issue
Telnet to Yahoo.com from your domain server
Send the test E-mail using Telnet command
After sending the mail you will get the exact error

Hope this helps.
mcjim2kAuthor Commented:
Looks like yahoo has blocked our IP based on the telnet response I got:

421 4.7.1 [TS03] All messages from x.x.x.x will be permanently deffered; Retrying will NOT success. See http://postmaster.yahoo.com/421-ts03.html

I have since submitted a request to be removed from this list.

Our server was recently attacked and was sending spam everywhere, this was probably the cause of being blocked by Yahoo, it has since been fixed.

Thanks a lot for the help.
mcjim2kAuthor Commented:
Got me where exactly where i needed to go.

Tony JLead Technical ArchitectCommented:
I was just about to post a link from Yahoo with some instructions:
Your error message is on there. Not sure how much help you'll find on the page but it's a start.
Tony JLead Technical ArchitectCommented:
And sorry to point out the obvious but if you were being used as a mail relay then 100% that's the cause of the blocking.
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