upgraded internet service to broadband - failed smtp connection

We have a single windows 2008 sbs running exchange, which was working fine.

We have just upgraded our internet service to fibre, and along with this came a new router and a new static IP address.

We have updated our DNS records so that our mail is forwarded to the new public IP, and when checking with mxtoolbox, I can confirm that this change has been implemented correctly.

We can connect using OWA, and we can send mail just fine.

We are not receiving mail, and I am aware that the change to our dns may take some time to replicate for everyone, but when we run the smtp diag within mxtoolbox, it fails.

I can see that the IP address it is trying to connect to is correct, and we have opened up the ports on our new router for 443, 25, 80, 3389, and 987.

I know that we may not need all of these open, but that is what we have right now, all forwarded on to the local IP address of our exchange server.

Is it just that I need to give it time to replicate, or now that mxtoolbox confirms the correct public IP address for our server, should the smtp diag now work OK?

If it should, how can I trap this rather frustrating problem. Any assistance, would be appreciated.

I have also tried the Microsoft Connectivity Analyser and this too fails, but does not give any reason for doing so??

Any ideas?
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When changing IP addresses, the first step is the firewall test:
Use on another PC/laptop SOMEWHERE ELSE (another ISP), and to the simple telnet test (really type this in:)
telnet new_IP_nr 25
ehlo test.com
mail from:test@test.com
rcpt to:real@yourdomain.com
subject: test


Open in new window

If that works, your firewall is ok.
Then proceed to test if the has been DNS updated yet. On that same computer/laptop:

set type=mx

check if IP has been updated or not.
If it has been updated, this ISP's webmail should already be able to send you email.
If not, more patience (could even take a whole day, starting from when you saved your DNS change).
Bunch of potential issues here.
DNS: did you make sure the MX records were updated?  Do you use a 3rd party spam filter?  
If you go to mxtoolbox.com, look up your MX records.  See if they are pointing directly at your server (it will show a FQDN like mail.mybiz.com or it may show 3rd party spam filtering service).  
Get your WAN IP, from home or outside the building, see if you can telnet into the SMTP server.
start a command prompt or putty..
telnet wan.ip.address -25
See if you get a response.
If you do, your ports are open.  If you don't, your ports aren't open.
Try the same thing from inside the building.
Get a response?  If so, your SMTP server is responding.

I'd check these simple things, the go from there.

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nigelbeatsonAuthor Commented:
many thanks to all. your comments both helped me to identify that our public IP had changed! we ordered a static IP, but unfortunately, we were still picking up a dynamic address which changed every time we restarted our router,

now we have that fixed, all is well.
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