SBS2011 exchange server not receiving SOME e-mail

We have a single sbs2011 server runing exchange, and is working pretty well for most things. However, we have some mail going astray, ie being sent by a couple of our clients, which never seems to arrive.

I have checked blacklists and SPAM settings, but everything seems OK.

On checking with we get the following responses :-

220 Microsoft ESMTP MAIL Service ready at Tue, 21 Aug 2012 11:23:16 +0100
OK - resolves to
Warning - Reverse DNS does not match SMTP Banner
 OK - Supports TLS.
 0 seconds - Good on Connection time
 OK - Not an open relay.
 5.897 seconds - Warning on Transaction Time
Session Transcript:

EHLO Hello []
 250-SIZE 10485760
 250 CHUNKING [156 ms]
 250 2.1.0 Sender OK [156 ms]
 RCPT TO: <>
 550 5.7.1 Unable to relay [5148 ms]
 221 2.0.0 Service closing transmission channel [140 ms]
Am I correct in that the line :-

OK - resolves to

should result in our mail server name, ie not, but

I have checked our own server smtp settings and all seem to be ok, but somone pointed me to get our service provider (talktalk) to add a reverse PTR to our account, but unfortunately, they do not seem to know what I am asking for.

Can anyone confirm whether I am on the right track here, and if so, what specifically do I need to ask for??

Any help gratefully received.

Many thanks.
Who is Participating?
Manpreet SIngh KhatraConnect With a Mentor Solutions Architect, Project LeadCommented:
Reverse DNS does not match SMTP Banner - Do you have a PTR record ?

As your service provider to check with MX and create PTR :) .... if the guy doesnt know ask him to get someone from Networking/DNS team or escalation :)

- Rancy
nigelbeatsonAuthor Commented:
I do not know if we have a revers PTR. I have taken over this server which has historically had this problem. I do not know how to access the ISP DNS, but no doubt I can get this information if we need it. I seem to recall though that in previous ocasions, this was something that the ISP had to do? Can you confirm?

I have hit a stone wall with TalkTalk support. They only seem to offer basic levels of support and when asked to escalate, he spoke with his manager who also did not know what I was talking about. I do not seem to be able to get past the first level support team.

Do you think I am on the right track though?? I am happy to persist if you think that this is the answer. I have asked other service providers to do this for me before, and they just asked for e-mail confirmation and it was done within a day or so.

Do you think that this will resolve our issue of the missing mail??

Manpreet SIngh KhatraSolutions Architect, Project LeadCommented:
I do not know how to access the ISP DNS - no once can they have to make changes.

I seem to recall though that in previous ocasions, this was something that the ISP had to do? Can you confirm? - Yes

maybe this current ISP isnt capable of anything :) So ask them to get more techincal person and share the error with them

Warning - Reverse DNS does not match SMTP Banner

Do you think that this will resolve our issue of the missing mail??- Possible

Ohk tell me this ..... if you dont see the email hit your Organization sender will get some NDR and we can try to work over it apart from that if an email doesnt hit your Organization gateway servers there isnt anything we can do :(

- Rancy
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nigelbeatsonAuthor Commented:
I will persist with TalkTalk (the ISP) to see if they can do this.

Unfortunately the sender does not receive an NDR, which has been the biggest part of the problem, as they are presuming we have recieved the e-mails (usually orders) and we get nothing, so we did not know they had sent them. This is obviously a very big problem for us, as they are one of our best customers!

We are using the ORF anti spam software on our server, which logs ALL incomming mail, so we know it is not actually getting to us, but when I research the diagnosis the fact that the reverse DNS does not match the SMTP banner, it indicates that it can cause this kind of problem.

It is the only thing that I can see that is even remotely a problem.

Thanks for your assistance.
David AtkinTechnical DirectorCommented:

I don't believe that the Reverse DNS is the issue.  I have a couple of customers who can't change the rDNS due to ISP restrictions - They don't have any problems.

Open the Exchange Management Console, go into Toolbox and use the tracking log explorer tool to see if you are actually reverencing the mail or not.

As a test, disable your ORF anti-Spam and ask your client to send a test email.

Check your clients domains on MXtoolbox and see if they are blacklisted.  May as well do the same for your own domain - Just to be sure.

If you can talk to your customers IT company, it maybe worth asking them to do an nslookup from their office and then telenet your server on port 25 to see if it actually gets a response.
nigelbeatsonAuthor Commented:
The problem only relates to a couple of clients that we know about. It is just unfortunate that it is one of their better ones that we are having problems with.

I have managed to get the call escalated now, and it sounds like we are moving in the right direction. The error reported from is the only problem area I can find, but if the new revers PTR does not fix it, we will have to resort to getting our client to track their message, as suggested earlier in this incident.

Our domain is not ony blacklists I can find, and if the work in hand does not produce any improvement, we will have to start checking their domain name too.

I will et you know as and when we get the PTR put in place, and what the outcome is.

Thanks to all.
Manpreet SIngh KhatraSolutions Architect, Project LeadCommented:
Make sure you get the Esclation guys to see what the Warning says on the mxtoolbox  .... maybe they might have some understand of it :)

No harm in getting them into this as well :)

- Rancy
nigelbeatsonAuthor Commented:
Yes, thanks. I provided them with full details of the report, so hopefully they will be able to check this too.

Many thanks.
nigelbeatsonAuthor Commented:
Many thanks.
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