Problems with sending emails in Outlook express

Posted on 2005-05-06
Last Modified: 2010-04-08
I get the following error when i try and send a message

The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was ''. Subject 'Test', Account: '', Server: '', Protocol: SMTP, Server Response: '550 5.7.1 Unable to relay for', Port: 25, Secure(SSL): No, Server Error: 550, Error Number: 0x800CCC79

I am running Server 2003, I have a Mail server(pop3, SMPT) configured. I am not behind a firewall, I DO HAVE "MY SERVER REQUIRES AUTHENTICATION" CHECKED.

My Domain:

I can send emails to my own account(localy,, I cant send emails to other accounts(

BUT, i sent one successful email to

I dont know how and i dont know why.

Please HELP!!!!
Question by:fsquared
    LVL 7

    Accepted Solution

    Try stopping and starting your default virtual smtp server.  If this doesn't do it you may need to a an SMTP connector pointing to your ISP server so to direct external emails to the outside world and not to try and resolve internally.
    LVL 7

    Expert Comment

    LVL 4

    Assisted Solution

    The receivers server is unable to verify that the senders address exists on the sending server. Your mail server is not configured up to standards.

    The recipient server is checking your server to validate the sender is allowed to send from that server. It is not finding that info, hence it thinks the mail is being relayed through the sending server by a 'spammer' basically.

    One thing that can cause this is if your server doesn't accept NULL senders. Make sure accept Null sender is on. Try sending through your ISP, probably works.

    I think the one email that you sent succesfully was because the recipients server is not checking for relayed mail. Spam magnet that :)

    Hope this helps.

    Assisted Solution

    I just fixed this issue for one of our remote users that was doing pop/smtp through an exchange server.  On the PIX firewall, the SMTP fixup had been turned on.  Strangely this was only happening on his desktop, his laptop was working fine.

    The command to change this is "no fixup protocol smtp 25"

    Hope this helps.

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