Postfix setup problems

[tony7671]

I'm really struggling with Postfix setup. I'm getting the probably with a non-existant domain for servers that check it - for example (domain name changed to "my-domain.co.uk"):

707974B8028: host mx01.1and1.co.uk[212.227.15.150] said: 421 invalid sender domain 'server1.my-domain.co.uk' (misconfigured dns?) (in reply to RCPT TO command)

The "hostname" command returns "server.my-domain.co.uk"

In the Postfix main.cf I have:

myhostname = post.my-domain.co.uk
myorigin = server.my-domain.co.uk

The thing that is mystifying me is where it is getting "server1.my-domain.co.uk". The VPS originally had a hostname of just "server1", but I can't find any references in the configuration files to "server1" - I've just no idea where it is getting that from, and it seems to be ignoring the configuration directives.

Any suggestions gratefully received,

Tony

[LibraOne]

I think that still there's something wrong with your network/hostname settings. Although it is a long time I installed Postfix, I did have similar issues when I wanted to change the hostname. So I think you are missing something.
What helped me at that time was to install Webmin. They have a page where you have an overview of your network and hostname settings. That quickly gave me insight in where I had left an unchanged field.