New ISP and DNS change, error 550 5.7.1 (Full Version)

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batfastad -> New ISP and DNS change, error 550 5.7.1 (21.Nov.2008 4:17:29 PM)

Hi guys

We have Small Business Server 2003 and we've been with the same internet provider for several years. It's a simple server setup, the only addon is AVG Exchange Server Edition.
We use an IPCop firewall box which provides DHCP and primary DNS services to our internal network. Our SBS 2003 server is a secondary DNS, and the DHCP service is disabled on the SBS machine. Having IPCop do our DNS/DHCP gives us more flexibility.

Last week we switched to a new internet provider, and I thought I'd got everything thought through properly but we're having some problems.

The morning our new broadband connection was activated, I changed the DNS records for our main business domain name.
I changed the A record for to point to our new static IP.
I also removed our old ISP's backup MX address, and added a new backup MX supplied by our domain hosting provider.

I changed the smart host in System Manager to our new ISPs SMTP relay. I did this in 2 places:
1) Default SMTP Virtual Server >  Properties > Delivery tab > Advanced button
2) Connectors > SmallBusiness SMTP Connector > Properties
In both cases I set it to the IP address in sq brackets, rather than hostname, of our new ISPs relay server.
I was advised it's better to have Exchange send through a relay rather than directly, because our IP address is in an ISP's range.

I also went into the SBS DNS MMC panel and changed the DNS forwarders, removing our old ISP DNS servers, and adding our new ISP DNS addresses. I've also had the OpenDNS servers listed in there for a while as well, just for backup purposes.

Sending mail to external addresses seems to be working perfectly.
However some external email addresses are having problems sending to our server. I've tried with different internet providers SMTP servers, GMail, Yahoo, and my personal reseller hosting account SMTP, and they all come through ok.

But one particular user has problems sending to us when using their personal ISP email address.
The bounce message they get is:
>Subject: failure notice
>Hi. This is the qmail-send program at
>I'm afraid I wasn't able to deliver your message to the following addresses.
>This is a permanent error; I've given up. Sorry it didn't work out.
> failed after I sent the message.
>Remote host said: 550 5.7.1 Requested action not taken: message refused

The bit is our correct static IP address.

But when they change their From address to be their work address which is one of our domain email addresses (, the message comes through ok.
They're a remote user who has a address which just forwards to their ISP email.

Are there any other places in Exchange where I need to change any settings to get the mail accepted?
The previous network admin left and I don't know that much about Exchange, apart from what I've learnt in the past year or so when needing to fix problems.

Any ideas/suggestions?
Cheers, Ben

batfastad -> RE: New ISP and DNS change, error 550 5.7.1 (24.Nov.2008 3:56:24 PM)

Ok I think I might have solved this now. Sender ID Filtering was set to Reject, and now I've set it to Accept and it appears to be working.
I'm certain it was also set to Reject before our change of ISP, and that user's email didn't bounce before.

Does anyone know why a change of ISP could have affected the behaviour of Sender ID filtering on our server?

Thanks, B

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