Issues accessing SMTP server from the internet...

[Robbo]

Hello All,
I have a fresh install of a standalone eBox server. All is working well but I can't send email using SMTP from a remote site. I can end and receive email on the local network. I get a 554 error in Outlook Express (which is relaying issue???). I have checked all my settings and all seem in order. My email client is saying that I am relaying messages but I am using TLS and you have to authenticate to send. I can receive messages ok.

There is a firewall and then my ebox server. I am using version 1.2 and have installed all modules and just disabled the jabber module and the firewall module because as I prefer to use separate firewalls.

What should I been checking? Is there any how-to's around? I have looked on the forums and have not found anything  that seems to be similar which is a little strange. Thanks in advance for any help.

Regards,
Robert.