On 5 August 2014 11:51, Barry Samuels bjsamuels@beenthere-donethat.org.uk wrote:
As a matter of interest I have changed outgoing mail to use mail.btinternet.com and it all seems to work perfectly now.
That, to me, implies a problem with United Hosting's servers although it doesn't explain why it still works perfectly on my old machine. I am in touch with United Hosting about this but they haven't yet come up with anything useful.
The combination of information you've given suggest to me that for some reason authentication was working before but is not working now.
A mail server that you try to relay through without authentication would respond the way you are seeing. It would likely, however, accept and deliver mail that it didn't need to forward (eg to other users on the same server).
On the other hand an ISP's mail server will generally accept all mail from their client's IP addresses without authentication. (Downside is that you have to live with whatever policies they implement, and if your PC is actually a laptop it will all break as soon as you move to a location outside your ISP's address range.)
I would be interested to know if the old PC works after you set it to use BT's relay. If it is authenticating correctly now, changing it to use BT's relay should fail (as the user/pass you have configured won't be accepted by BT's server), although it may just fallback to unauthenticated.
I still think that your logs should give you the answer - same test on both old and new PCs and see how the logs differ. Even if there are no obvious errors this should tell you what they're doing differently.
Mark