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SMTP Relay Issue "550 5.7.1"

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SMTP Relay Issue "550 5.7.1" - 1.Jul.2008 11:39:31 AM

parkjeo2

Posts: 5
Joined: 1.Jul.2008
Status: offline

It is first time post this forum. I am glad to know this.
Receiving is fine, only cannot sending email to external domain.

My problem is this.
I have been having error message " 550 5.7.1 Unable to relay for for username@domainname.com".

for outside user, I setup outlook using pop3.
It seems to not authenticate when sending external domain.
interal domain is fine(internal domain1 to internal domain2)
I hosting couple domain for emails.

I also check smtp setting on ESM. As you know, We dont want relay open for exchange. if I take off limitation on relay option. emails are perfect(sending,receiving quickly). I know this mean security holes.(spam something)

I have spent whole week for this stupid error.
OWA is fine from anywhere.

So I narrow down this to Authentication issue on SMTP specially Relaying.

Any ideas would great appreciated.
Thanks

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RE: SMTP Relay Issue "550 5.7.1" - 1.Jul.2008 12:26:46 PM

uemurad

Posts: 5488
Joined: 7.Jan.2004
From: California, USA
Status: online

You may already understand this, but relaying means the message is being delivered to a system that isn't the authority for that domain. For example, if you wanted to send a message to a yahoo.com address and sent the message to my system, that's a relay attempt. My system won't allow you to relay and would reject the message.

So the question is, where is the message being delivered (the system denying the relay), and why is it going there instead of its authoritative system?

Does this happen for all outbound external messages, or just to a limited set of domains?

Has this ever worked? If so, what has changed since?

The most likely cause for this is that you are directing your outbound messages using a SmartHost, either in a SMTP Virtual Server or an SMTP connector, and that the smarthost isn't configured to relay (either at all, or just from your system).

_____________________________

Regards,

Dean T. Uemura
Microsoft MVP - Exchange
exchangeguy.blogspot.com
uemurad@yahoo.com

(in reply to parkjeo2)

Post #: 2

RE: SMTP Relay Issue "550 5.7.1" - 1.Jul.2008 12:38:39 PM

parkjeo2

Posts: 5
Joined: 1.Jul.2008
Status: offline

Thanks for reply.
SMTP is default since i installed from scrach. i don't have smathost setup.
I think that how to relay my own domain to send email is the key for this.

So the question is, where is the message being delivered (the system denying the relay), and why is it going there instead of its authoritative system?
=>I cannot quite understand. could you explain more?

Does this happen for all outbound external messages, or just to a limited set of domains?
=> yes, all outbound external messages got same.

Has this ever worked? If so, what has changed since?
=> Most of users use OWA before. since we have NDR attacked couple months ago. I did add recipient filter option.

Still no clue.

(in reply to uemurad)

Post #: 3

RE: SMTP Relay Issue "550 5.7.1" - 1.Jul.2008 1:41:43 PM

uemurad

Posts: 5488
Joined: 7.Jan.2004
From: California, USA
Status: online

quote:

So the question is, where is the message being delivered (the system denying the relay), and why is it going there instead of its authoritative system?
=>I cannot quite understand. could you explain more?

Does this happen for all outbound external messages, or just to a limited set of domains?
=> yes, all outbound external messages got same.

Since all outbound external messages are affected, the likely cause in my opinion is still a smarthost setting. This can be configured in one of two places.

The first is in the Default SMTP Virtual Server setting. Open the ESM and expand to your server, Protocols, and SMTP. Open the properties of Default SMTP Virtual Server, go to the Delivery tab, click on Advanced. Note if there is anything in the SmartHost field.

The second is found in the SMTP connectors. You need to check each connector (there may be only one). On the General tab of the connector properties, note whether the DNS radio button is selected or the Forward all mail button is selected.

Keep in mind that a smarthost does not necessarily have to be in your environment. Some ISPs require you to send all messages to one of their servers.

quote:

Has this ever worked? If so, what has changed since?
=> Most of users use OWA before. since we have NDR attacked couple months ago. I did add recipient filter option.

My question was about whether outbound mail worked before, but what else (if anything) did you configure after your NDR attack? Recipient filtering affects inbound messages.

Finally, I'd suggest you use telnet to test outbound communications. I wrote some instructions you can follow.

_____________________________

Regards,

Dean T. Uemura
Microsoft MVP - Exchange
exchangeguy.blogspot.com
uemurad@yahoo.com

(in reply to parkjeo2)

Post #: 4

RE: SMTP Relay Issue "550 5.7.1" - 1.Jul.2008 4:35:40 PM

parkjeo2

Posts: 5
Joined: 1.Jul.2008
Status: offline

I tested smpt communication as you recommend. it said "unable to relay for ~!"
it is same error i had. it looks pretty nice blog thanks.

Since I have digging some setting on ESM, I changed this

In ESM,
" SMTP properties>Authentication>both check basic authentication and intergated windows authentication."

All email are ok to send/receive. But if i enable TLS encryption, it fails again.
I don't want to only check basic authentication in case of sniffing.

Thanks

_____________________________

Automated alerting and response
Pro-active approach to the entire problem.

(in reply to uemurad)

Post #: 5