an smtp protocol error occured

Posted on 2006-03-22
Last Modified: 2008-01-09
Hi All,

I have a problem about sending mail: I have a Exchange 2000 Server/ windows 2000 server. It almost complete except for messages to and a few other domains sit in queue in retry mode.  If I check the properties of the queue it says that An SMTP protocol error occurred.  I send mail to, then i receive mail Delivery Status Notification (Delay) and mail undelivery from postmaster@mydomain. I check yahoo mail and not receive mail from my domain.  I'm at a loss!  Help me please!!
Thank in advance
Question by:cloudycun
    LVL 2

    Accepted Solution

    Yahoo simply doesn't like your server.  

    Check the basics:  
    1) Do you have a proper reverse DNS entry (PTR) for your server's IP, meaning the IP it presents itself to the world as?
    2) Are you on an RBL- check and 'spam database lookup' at and put in the address mentioned in step #1.

    Also- you probably also have problems sending to AOL, I'd be surprised if that wasn't the case.

    LVL 104

    Assisted Solution

    If you are on a DSL connection or dynamic IP address, then you will probably have email delivery problems. You will need to use an SMTP Connector to route through your email through your ISPs SMTP Server.

    Otherwise check that everything matches - DNS, reverse DNS and what the server announces itself as.

    Finally I have seen these sorts of problems caused by firewalls. If you have a firewall (what am I saying cos you will have a firewall), check whether it has any kind of SMTP scanning features and if so, disable them.


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