Announcement

Collapse
No announcement yet.

551 This is not a relay host - POP3

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • 551 This is not a relay host - POP3

    Okay so I we are running Exchange 2003 SP2. We have 13 remote locations and 1 corporate location. Everyone remotely, was set up to use OWA(not my choice), which I think was a complete disaster. I am in the process of phasing all these people over to POP3, however, if user x tries to sending to a recipient OUTSIDE the company domain. It IMMEDIATELY gets rejected with the following error:

    551 This is not a relay host - mail must be to or from host domain.

    If sending to within the company domain(even though the remote offices dont authenticate through our AD) it works fine. But outside the @company.com address, is a no go.

    We have the outgoing smtp listed as mail.XXXX.net and incoming as 204.x.x.x (actual ip address held for security reasons).

    Any thoughts/suggestions?

    Thanks!
    Last edited by SZupek; 16th June 2008, 22:02.

  • #2
    Re: 551 This is not a relay host - POP3

    Seriously, without offence I will skip the whole "Why on earth are you using POP3" as I can't think of a non-sarcastic way of asking it. Why don't you look at purchasing a certificate and using RPC/HTTPS instead, even OWA is better than POP3 (minor niggles aside as OWA is web based).

    AND

    I completely agree with withholding IP details but it is best to change the domain name as well because it is really easy to find it in 2 seconds if that is left.

    Like this:
    Originally posted by SZupek View Post
    We have the outgoing smtp listed as mail.cXXc.net and incoming as 204.x.x.x (actual ip address held for security reasons).
    Anyway....

    Exchange 2003 uses IIS for its SMTP engine therefore it would be good to check the domains part on this server. If you open the default SMTP virtual server and check your domains are listed in there first.
    cheers
    Andy

    Please read this before you post:


    Quis custodiet ipsos custodes?

    Comment


    • #3
      Re: 551 This is not a relay host - POP3

      Do you have some better solution for users that are outside of our Domain to be able to access, edit, create ,etc with the same ability that outlook offers? OWA is great when you are out of the office, but these people always work remotely and having them use OWA as their main access is a joke.

      Doesn't IIS just control the OWA portion? I am trying to get users into Outlook, not use online. Are you saying even exchanges SMTP service is controlled by IIS?

      I simply dont know enough about the HTTPS solution and its not a high priority since people can up and run accordingly. Could our Certificate Server just assign a public certificate? Then we would just have to open port 443 (or whatever it is, 995 maybe) and it would magically be better?

      Comment


      • #4
        Re: 551 This is not a relay host - POP3

        First - the error message you are getting is not an Exchange message. Therefore it is being generated by something else.

        As already indicated, the preferred remote access solution is RPC over HTTPS. This provides the full Exchange experience for remote users through a single port - 443. POP3/IMAP should be the last choice for remote access.

        A commercial SSL certificate should really be used - not a self generated certificate - even from your own CA. This avoids any issues with trust and certificate prompts.

        Instructions for setting up RPC over HTTPS vary, mine are at http://www.amset.info/exchange/rpc-http.asp

        The major reasons for not using POP3 is that you lose all of the central backup solutions. The email is stored in a PST file which is practically impossible to backup. With remote users this is even more important as they are at more risk of data loss.

        Simon.
        --
        Simon Butler
        Exchange MVP

        Blog: http://blog.sembee.co.uk/
        More Exchange Content: http://exchange.sembee.info/
        Exchange Resources List: http://exbpa.com/
        In the UK? Hire me: http://www.sembee.co.uk/

        Sembee is a registered trademark, used here with permission.

        Comment


        • #5
          Re: 551 This is not a relay host - POP3

          Sembee I appreciate you taking the time to create that tutorial, this is completely new information to me and does seem like the best option. However I do have a ? regarding the PRINCIPLE NAME FOR THE PROXY SERVER.

          is it literally supposed to be "mssdt: <companys exchange html location>"?

          for instance our exchange server is http://webmail.company.com/exchange

          so I would put "msstd:webmail.company.com/exchange"?

          Since this is the first i've heard of HTTPS/RPC its all new to me.

          Thanks again for taking the time to answer and create that tutorial.

          Comment


          • #6
            Re: 551 This is not a relay host - POP3

            I believe my instructions state it is nothing but the name. SO if your SSL certificate is issued to mail.doamin.net then it is

            msstd:mail.domain.net
            no / anything, or http - just the host name.

            Simon.
            --
            Simon Butler
            Exchange MVP

            Blog: http://blog.sembee.co.uk/
            More Exchange Content: http://exchange.sembee.info/
            Exchange Resources List: http://exbpa.com/
            In the UK? Hire me: http://www.sembee.co.uk/

            Sembee is a registered trademark, used here with permission.

            Comment

            Working...
            X