Windows NT - Running some sort of mail server, 550 not permitted

Posted on 2005-04-09
Last Modified: 2010-03-18

We had to swap the internet from a BT ADSL feed, to One Tel today.

Their was a main Windows NT Server that everything seemed to be recieving IP addresses from, linked to a router I could not get any details for.

The Server IP before the change was, and had a gateway of

We purchased a new router and set all machines including the server to obtain IP automatically.

All machines can pick up IP address - but know we are unable to send external email from any of the machines.  

We noticed that on the client machines outlook was set to connect to, with the auto config the server IP had changed to - we updated all clients so now outlook opens.  The problem is that we are unable to send external emails or recieve any external mails.

The server now has an IP of , with a gateway of (The new router we have installed)

When we send an email - it comes back to the inbox, within the message it states

"550 Relay not permitted"

Any ideas on what it could be

Question by:Secureconcepts
    LVL 6

    Accepted Solution

    The problem is the ISP doesnt allow mail relay. that is you to send mail to their mail server to send out to a 3rd party mail server. the way around this is to get SNMP and POP3 server information from the mail provider and enter that directly to the clients, and have them login to the SNMP servers directly, rather than having your server act as a relay.

    without detail on how your mail is setup (ie are you hosting it? is the company you get dsl from hosting it? etc) I cannot assit your furthur.

    what you need to know:

    who hosts your email service?
    does the One Tel isp allow you to talk to other mail servers outside their network?
    does your mail service provider accept connections from outside their network?

    Author Comment

    Will find out SNMP and POP 3 info from the Mail Provider - thanks

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