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Send Error - #5.5.0 smtp;503 This mail server requires ... - 5.Nov.2008 5:13:16 PM

Nyn11Tech

Posts: 3
Joined: 5.Nov.2008
Status: offline

We receive these mail rejects periodically from only one recipient. All other mail works fine and has been fine for 4 years. When we receive this reject, subsequent mail to this recipient works for one to several days, then we get a reject again. It may actually reset daily - we are a 24-hour operation so it is difficult to tell. We will get these rejects for mail sent to any user in the recipient's domain.

The reject message we get is:

The following recipient(s) cannot be reached:

Sample User on 11/3/2008 9:34 AM
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<email.int.ourdomain.org #5.5.0 smtp;503 This mail server requires authentication when attempting to send to a non-local e-mail address. Please check your mail client settings or contact your administrator to verify that the domain or address is defined for this server.>

We are running MS Server 2003 running Exchange Server 2003 SP2.

The recipient is using a Barracuda device and says when this happens he does not see the mail even hitting his filter.

I can successfully perform an NSLookup internally and it resolves to the recipient correctly.

Any ideas would be GREATLY appreciated.

Post #: 1

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RE: Send Error - #5.5.0 smtp;503 This mail server requi... - 5.Nov.2008 7:41:32 PM

Sembee

Posts: 4093
Joined: 17.Jan.2008
From: Somewhere near London, UK
Status: offline

Usually this happens when the recipient has multiple MX records in their DNS, and one of them isn't valid. Other times I see it with large ISPs where they are using a cluster and one of the cluster isn't working correctly.

You need to look at your SMTP logs to see what IP address the traffic is going to and being rejected. That will give you a clue which you can then take to the other side.

Simon.

_____________________________

Simon Butler,
Exchange MVP
Blog: http://blog.sembee.co.uk/
Web: http://www.amset.info/
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(in reply to Nyn11Tech)

Post #: 2

RE: Send Error - #5.5.0 smtp;503 This mail server requi... - 6.Nov.2008 1:30:58 PM

Nyn11Tech

Posts: 3
Joined: 5.Nov.2008
Status: offline

Thank you for the reply - it led me straight to the problem.

I checked our SMTP logs and found the mail is being sent - by us - to a totally incorrect IP address. It seems we are resolving it wrong on the first attempt, but subsequent attempts get it right.

Looks like a DNS issue, but I am wondering if our recipient needs to check with whomever is hosting their DNS and MX records (Network Solutions), or if it is something in their ISP (from whom they purchased their public IP block).

Also - I asked our recipient (the one who we are trying to send to) if anyone else is getting mail to them rejected. At first they said "no", but now they have checked and it looks like it is not just us. I have no deatils yet, but am I correct that it is on their end, or could it still be something with us? We have this issue with nobody else - ever.

Thank you again!

(in reply to Sembee)

Post #: 3

RE: Send Error - #5.5.0 smtp;503 This mail server requi... - 7.Nov.2008 10:31:39 AM

Sembee

Posts: 4093
Joined: 17.Jan.2008
From: Somewhere near London, UK
Status: offline

The only thing I can suggest is that you use some of the public tools to see what their MX records resolve as, then what the host names resolves to. Compare that to an internal nslookup. If they are the same, but there is an error in the records then the recipient needs to resolve that issue. If it is occurring with other senders, then as long as there are no other similarities (such as you and the other sender are on the same ISP) it would be point to an issue the recipient needs to resolve.

Different servers react in different ways to errors, which would explain why some people have the error and others do not.

Simon.

_____________________________

Simon Butler,
Exchange MVP
Blog: http://blog.sembee.co.uk/
Web: http://www.amset.info/
In the UK? Hire me: http://www.sembee.co.uk/
Exchange Resources: http://exbpa.com/

(in reply to Nyn11Tech)

Post #: 4

RE: Send Error - #5.5.0 smtp;503 This mail server requi... - 14.Nov.2008 10:53:47 AM

ganesh1990_ece

Posts: 2
Joined: 10.Nov.2008
Status: offline

I would suggest that its better to trace the path of the mail .And check where it is rejected through,use the trace route command to trace the path of the router connecting the client's ISP.

also check the SMTP connection
Thanks and regards

(in reply to Nyn11Tech)

Post #: 5

RE: Send Error - #5.5.0 smtp;503 This mail server requi... - 14.Nov.2008 11:52:20 AM

Nyn11Tech

Posts: 3
Joined: 5.Nov.2008
Status: offline

Problem solved - though we are not sure quite how.

The recipient checked with their DNS host who said they found no problems. Within 2 hours of this conversation the problem disappeared and has not resurfaced.

We think there may have been a second (bad) MX record, or a problem with the Host A record or similar that someone corrected, but isn't fessing up to.

Thanks to all for your insightful suggestions!

(in reply to ganesh1990_ece)

Post #: 6

RE: Send Error - #5.5.0 smtp;503 This mail server requi... - 14.Nov.2008 11:59:36 AM

Sembee

Posts: 4093
Joined: 17.Jan.2008
From: Somewhere near London, UK
Status: offline

quote:

ORIGINAL: Nyn11Tech

The recipient checked with their DNS host who said they found no problems. Within 2 hours of this conversation the problem disappeared and has not resurfaced.

We think there may have been a second (bad) MX record, or a problem with the Host A record or similar that someone corrected, but isn't fessing up to.

That happens a lot.
ISPs will never admit to there being a problem. I have been on the phone to them with fire alarms going off in the background "no problem here sir".
However someone will look and find the issue and it will magically start working correctly. You call the ISP and they will deny any changes have been made.

I operate a simple rule when talking to ISP support. Presume that they are lying. Life is much easier that way.

Simon.

_____________________________

Simon Butler,
Exchange MVP
Blog: http://blog.sembee.co.uk/
Web: http://www.amset.info/
In the UK? Hire me: http://www.sembee.co.uk/
Exchange Resources: http://exbpa.com/

(in reply to Nyn11Tech)

Post #: 7