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MS Exchange Server - SMTP relay problem

By Sharad Sreedharan ·
Hello,

I hope somebody would be able to help. Let me try to explain the network setup I've.

The exchange server is behind a PIX firewall, the PIX permits POP3 & SMTP connections.

I've setup an Exch 5.5 with the following configuration whichideally should allow authenticated users to use POP3 to download
and SMTP to send emails for outside addresses.

- POP3 is enabled on the server.
- For the IMS propteries --> 'Routing' screen,
'Reroute incoming SMTP mail' is ENABLED. Under the 'Routing Restrictions' tab, checkboxes for 'Hosts and clients that successfully authenticate' & 'Hosts and clients with these IP addresses' have been checked.

POP3 is working fine, SMTP does not.

When roaming users' (using local ISP dial-up) from the Internet try to send email (using the Exchange Server SMTP) to outside
email addresses, the server logs the following error:

Event I 4188
Source: MSExchangeIMC
Type: Error
Category: SMTP Interface Events

Description:
Refused to relay <xxxx@hotmail.com> for xxx.xxxx.net.xx(<ip number&gt


The clients are mostly 'Microsoft Outlook Express' / 'Microsoft
Outlook'.

On the client side, for Microsoft Oultook Express the error message is
as follows:

The message could not besent because one of the recipients was
rejected by the server. The rejected e-mail address was
'xxxxxx@hotmail.com'. Subject 'test email', Account: 'xxxxxx', Server:
'xxxx.x.com', Protocol: SMTP, Server Response: '550 Relaying is
prohibited', Port: 25, Secure(SSL): No, Server Error: 550, Error
Number: 0x800CCC79


But, when I try to use POP3 and SMTP settings to the same server from the internal network, I'm able to send emails to outside addresses.

I'm not sure why it's not permitting users' conncted to Internet to (ISP dial-up) send emails using the account configured on the Exchange
Server?

Help appreciated.

Thanx in advance.

Sharad

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MS Exchange Server - SMTP relay problem

by NetTek In reply to MS Exchange Server - SMTP ...

Many Exchange administrators incorrectly configure Exchange's mail relay options. First and foremost, make sure you have the latest service pack installed. Second, a mail relay means that your Exchange server will accept Internet mail, and then reroute it to another SMTP server on the Internet.

As far as "reroute incoming SMTP mail" is concerned, this should be checked, and the "Sent to:" should be your_domain.com and the "Route to:" should be inbound. This is what allows incoming mail to get to reciepients@your_domain.com.

Under routing restrictions, DO NOT check "hosts and clients that successfully authenticate." This has nothing to do with email that is coming into your local network. It means that you have another security mechanism in place, and the incoming mail must authenticate in order for your server to reroute it to another SMTP server on the Internet.

Additionally, you do not need to have anything under "Hosts and clients with these IP addresses". Again, if you are not relaying mail as defined above, you do not need this option either.

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MS Exchange Server - SMTP relay problem

by Sharad Sreedharan In reply to MS Exchange Server - SMTP ...

Hi NetTek,

Thanks for the reply.

I guess probably my explanation was improper OR it has been misinterpreted.

What I'm trying to achieve with my exchange server is that it will accept all emails destined to reciepients@mydomain.com AND blockall SMTP relay except those authenticated clients/hosts which are trying to sent email to outside email addresses (these would be basically the POP3 users in my organisation).

I believe with the settings I've specified, the Exchange Server would achieve what I'm trying to do. Does it work that way? I thought so.

Any ideas/suggestions on the configuration?

Help appreciated.

Regards, Sharad

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MS Exchange Server - SMTP relay problem

by NetTek In reply to MS Exchange Server - SMTP ...

Did you configure the "My mail server requires authentication" option in Outlook Express on your clients?

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MS Exchange Server - SMTP relay problem

by Sharad Sreedharan In reply to MS Exchange Server - SMTP ...

Hi NetTek,

Thanks for the reply.

I had tried to configure the setting on authentication for MS Outlook as well as Outlook Express, but still no luck!!

Hope there is a solution to this.

Regards,

Sharad

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MS Exchange Server - SMTP relay problem

by Sharad Sreedharan In reply to MS Exchange Server - SMTP ...

This question was closed by the author

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