Email fails with: 550 Warning - Reverse DNS lookup failed for host
Hello,
I am having a problem emailing a particular person, the email worked fine last week, but now when I try, I get this message back from my server:
-----------------------
Your message did not reach some or all of the intended recipients.
Subject: Conference
Sent: 03/10/2007 16:36
The following recipient(s) cannot be reached:
'email - deleted for privacy'' on 03/10/2007 16:36
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<my email domain here #5.5.0 smtp;550 Warning - Reverse DNS lookup failed for host My server static IP here.>
I would appreciate some help to work out why.
When I check my domain for reverse DNS here: http://www.mxtoolbox.com/diagnostic.aspx it comes back ok..
Thanks
Jack
I am having a problem emailing a particular person, the email worked fine last week, but now when I try, I get this message back from my server:
-----------------------
Your message did not reach some or all of the intended recipients.
Subject: Conference
Sent: 03/10/2007 16:36
The following recipient(s) cannot be reached:
'email - deleted for privacy'' on 03/10/2007 16:36
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<my email domain here #5.5.0 smtp;550 Warning - Reverse DNS lookup failed for host My server static IP here.>
I would appreciate some help to work out why.
When I check my domain for reverse DNS here: http://www.mxtoolbox.com/diagnostic.aspx it comes back ok..
Thanks
Jack
ASKER
My result is:
telnet <exchange public IP> 25
Trying <exchange public IP>...
Connected to email.co.uk.
Escape character is '^]'.
220 infomedltd.co.uk Microsoft ESMTP MAIL Service, Version: 6.0.3790.3959 ready at Wed, 3 Oct 2007 21:48:25 +0100
So, I have a problem...how can I solve it?
Thanks
telnet <exchange public IP> 25
Trying <exchange public IP>...
Connected to email.co.uk.
Escape character is '^]'.
220 infomedltd.co.uk Microsoft ESMTP MAIL Service, Version: 6.0.3790.3959 ready at Wed, 3 Oct 2007 21:48:25 +0100
So, I have a problem...how can I solve it?
Thanks
ASKER
Sorry, meant to change above, all instances of infomedltd.co.uk to email.co.uk - I guess it doesnt matter too much..
I don't find any MX records for that domain anyway, so that could be a problem.
This is my guide on DNS configuration for an Exchange server, it should help:
http://www.amset.info/exchange/dnsconfig.asp
Simon.
This is my guide on DNS configuration for an Exchange server, it should help:
http://www.amset.info/exchange/dnsconfig.asp
Simon.
ASKER
Hi Simon,
Not sure why you cant see the MX records for the infomedltd.co.uk - works for me: http://www.mxtoolbox.com/index.aspx
I did the SMTP telnet test - all OK.
The FQDN in Exchange System Manager is "infomedltd.co.uk" - not "mail.infomedltd.co.uk" as is written in your article.
If you check my MX record, you will notice that the instruction is to send it to infomedltd.dyndns.org (a service from http://www.dyndns.com as I am sure you know). The setting in DYNDNS then forward the email to the public IP address of my Exchange.
Is the above likely to cause a problem?
Should I be checking the reverse DNS setting for the domain name, or for the exchange public IP?
The result for the public IP of echange server from: http://www.dnsgoodies.com/
Server: 192.168.2.124
Address: 192.168.2.124#53
Non-authoritative answer:
234.106.73.194.in-addr.arp
Thanks
Jack
Not sure why you cant see the MX records for the infomedltd.co.uk - works for me: http://www.mxtoolbox.com/index.aspx
I did the SMTP telnet test - all OK.
The FQDN in Exchange System Manager is "infomedltd.co.uk" - not "mail.infomedltd.co.uk" as is written in your article.
If you check my MX record, you will notice that the instruction is to send it to infomedltd.dyndns.org (a service from http://www.dyndns.com as I am sure you know). The setting in DYNDNS then forward the email to the public IP address of my Exchange.
Is the above likely to cause a problem?
Should I be checking the reverse DNS setting for the domain name, or for the exchange public IP?
The result for the public IP of echange server from: http://www.dnsgoodies.com/
Server: 192.168.2.124
Address: 192.168.2.124#53
Non-authoritative answer:
234.106.73.194.in-addr.arp
Thanks
Jack
ASKER CERTIFIED SOLUTION
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ASKER
Hi Simon,
Many thanks, I will follow that list and complete.
Thought I should mention, this seems an issue with only one user as I notice today, I can send to the person whos email kept failing with: <my email domain here #5.5.0 smtp;550 Warning - Reverse DNS lookup failed for host My server static IP here.>
and today, another email address which she cant send to, but one which I can, the error is:
Your message did not reach some or all of the intended recipients.
Subject: Booking Confirmation
The following recipient(s) cannot be reached:
recipientsname@hotmail.com
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<bay0-mc10-f23.bay0.hotmai
Could it be that this users mailbox is corrupt?
Jack
Many thanks, I will follow that list and complete.
Thought I should mention, this seems an issue with only one user as I notice today, I can send to the person whos email kept failing with: <my email domain here #5.5.0 smtp;550 Warning - Reverse DNS lookup failed for host My server static IP here.>
and today, another email address which she cant send to, but one which I can, the error is:
Your message did not reach some or all of the intended recipients.
Subject: Booking Confirmation
The following recipient(s) cannot be reached:
recipientsname@hotmail.com
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<bay0-mc10-f23.bay0.hotmai
Could it be that this users mailbox is corrupt?
Jack
Why would you think the mailbox is corrupt? The NDR has been generated by a server at Hotmail. It has nothing to do with your server.
Simon.
Simon.
I think the bounce message is generated by the sender server, but it refers to the hotmail server as responsible for giving the 550 failure.
Either the user doesn't exist, or the username (adressee) is misspelled, or there's another type of rejection taking place but the failure message is not "spot-on".
/RID
Either the user doesn't exist, or the username (adressee) is misspelled, or there's another type of rejection taking place but the failure message is not "spot-on".
/RID
ASKER
I think this because, I am able to send to this hotmail address but my colleague is not, to me that suggests the problem is with my colleagues mailbox. I know the hotmail address exists as we were replying to a message sent to us.
Other thoughs are that Sophos and PureMessage could be affecting things. I will keep an eye.
Jack
Other thoughs are that Sophos and PureMessage could be affecting things. I will keep an eye.
Jack
I get this error from ing.wanadoo.es even though I do have a reverse DNS entry. I wonder if some mail hosts look up the reverse DNS entry and then take the FQDN and see if the forward entry matches (which is not the case for me)
Again, i verified that latinmail.com's dns server (wanadoo) could look up my DNS entry in reverse, but the problem still occurs. The problem doesn't occur on a mail server whose reverse DNS entry and forward DNS entry match.
Again, i verified that latinmail.com's dns server (wanadoo) could look up my DNS entry in reverse, but the problem still occurs. The problem doesn't occur on a mail server whose reverse DNS entry and forward DNS entry match.
Have you tested the reverse DNS using some of the online tools?
Does the reverse DNS entry match how the Exchange server announces itself?
You can see that by telnetting to port 25 of the Exchange server
telnet servername 25
and see what the banner says. If it says domain.com (instead of host.domain.com) or domain.local then you have a problem.
Simon.