Problem with mail forwarding to external contacts with Exchange 2010: Error 550 not permitted

Exchange 2010 on SBS2001.
Mail flow through BTconnect works fine, except for emails we try to forward to external contacts, which bounce to the sender with ‘ #550 Not permitted’. I’ve found 3 possible solutions on various forums, namely:
Which I implemented but it didn’t help;
2) Call BT and have them add the sending domain to BT Mail Relay;
3) A workaround involving routing emails via DNS and setting up a reverse DNS record. I’ve heard of reverse DNS but never attempted to set it up, it’s always mystified me.
Grateful for any advice on either these or any other possible solution.
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AmitIT ArchitectCommented:
You need to enable Auto Forward at org level. Then it will work. By default it is not enabled.
Simon Butler (Sembee)ConsultantCommented:
BT's relaying servers aren't great. They have all sorts of restrictions on them.
If you have a static address from BT, then I would get a PTR (aka reverse DNS) configured. This isn't something that you do - you have to ask BT.

To setup a PTR, you need to use a form on BT's web site. 

(If that link breaks - Google for BT reverse DNS).

You need to give them the host name that resolves to your server - with SBS that is usually
Once the change has been made (use an online tool to check the PTR against your static address) change the Send Connector to route by DNS.


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