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Can't send Outlook message via private domain to any Yahoo Account?

I use Outlook to send and receive emails from my domain. I also have a Yahoo account. When I send emails to any Yahoo account (and this only occurs with Yahoo accounts) from my domain, the bounce back a day or so later with the following message: Could not deliver message to the following recipient(s): Failed Recipient: [PrivateAccount]@yahoo.com Reason: Remote host said: 451 Message temporarily deferred - 4.16.50 -- The header and top 20 lines of the message follows -- Received: from c-71-227-49-46.hsd1.mi.comcast.net [71.227.49.46] by mail.mysmartermail.net with SMTP; -- truncated -- I have no problems sending an email from my Yahoo account to my domain account, but can send an email back and receive it. I checked with the domain host server company and they couldn't find any problems and no one else has reported a problem. This has been on-going for about a week. Anyone have a suggestion? TIA. Jayson LVslotdoc, Please re-read my post carefully and then let me know if you have a solution. Your post is not applicable, but thank you for your time.

Public Comments

1. The free Yahoo Mail service does not include incoming/outgoing POP mail service. You will have to upgrade to Yahoo Mail Plus or one of the other premium services in order for Yahoo Mail to work through your mail reader program, or your primary POP3 mail server. Yahoo Mail Plus costs $20/year, you can find out more by clicking the link below. http://mailplus.mail.yahoo.com
2. Hi Jeff, Recently Yahoo has started "greylisting" almost every email that goes through their mail server. Greylisting is a way of attempting to block SPAM. Yahoo mail denies the first delivery attempt of an email (451 Message temporarily deferred - 4.16.50). They assume that SPAMers don't try sending the same email twice, so they put the ip address of that email server on a list and then if the delivery is retried within a short amount of time, they assume that it is a good email. So we believe in next retry it should deliver and also in error message itself it denotes that it is a temporary problem so it may be due to communication problem. Thanks, Rubal Jain
3. Can anyone confirm Rubel's answer? he's copied and pasted it on every thread related to the 4.16.50 error. Its plausible, but i can't find any other confirmation from other sources that his answer is indeed the case.
4. Griffonage, No, I can't confirm it, and it doesn't make any sense. $ telnet mx1.mail.yahoo.com 25 Trying 4.79.181.14... Connected to mx1.mail.yahoo.com (4.79.181.14). Escape character is '^]'. 451 Message temporarily deferred - 4.16.50 Connection closed by foreign host. If it were a greylisting problem, I wouldn't be getting disconnected until after the sending and receiving envelopes were sent. A better guess is that we are being rate-limited and can only make 50 connections an hour (the number 50 is a guess). If I go to another host with a different IP and do my telnet test, it appears to work properly.