Mail sent from smtp agent sometime being rejected

[clusters]

Hello,

We are in a little problem here. Some of our customers use AT&T/SBCGlobal emails and messages we sent to them are rejected as we use the SMTP mail agent to send our emails. Our Sugar is host on a 192.168.x.x server and it is behind a firewall with a public IP address, and our mail server is hosted on a public server where we have authentication setup for mail relay.

The problem seems emails sent out from Sugar get the private hostname and the public firewall address as the originated from, and it is probably not passing the AT&T filter with data format error (again mails are relayed form our public hosted server with another hostname and IP).

Anyone has any idea on how I may be able to fix this? Do yo think by adding our firewall's public IP to our DNS would help? But we still would have a prblem with the hostname? Any hlep are greatly appreciated. Thanks!

Regards,

Tim

P.S. Before we converted to Sugar we use MS Outlook and the same public mail server to relay our mails and we didn't recall to have problems with AT&T. So I suspect this may have some to do with how Sugar put together the mail header?