EFW Support

We are currently using the EFW as a spam scanner/smtp proxy for an exchange server. The FQDN of the Exchange server + External IP/DNS/MX + PTR are all the same: remote.blah.com
If I set the SMTP_HELO name to be remote.blah.com (smtp banner should be the same as the MX/PTR to avoid spam issues when sending) then I end up with
"Jul  9 16:18:35 postfix/smtpd[27442]: NOQUEUE: reject: RCPT from xxxl-xxxl--1x50-151.net24.it[.xx..]: 450 4.1.1 <info@blah.com>: Recipient address rejected: undeliverable address: mail for [10.x.x.x] loops back to myself; from=<xxxxxxxxxxx@xx.com> to=<info@blah.com> proto=ESMTP helo=<device.lan>"
issues as the exchange and EFW have the same name.

I can't change the FQDN of the exchange server/MX/PTR without causing issues for outlook web access and some other services.

The current workaround is to manually edit the main.cf postfix file to give different hostname and SMTP_HELO names but making any subsequent change to grey/white/black listings overwrites these changes and I need to manually copy in the main.cf and restart.
The device is named firewall.blah.local for AD purposes (web proxy is also enabled) so it would be good to have the hostname = firewall.blah.local and have the SMTP_HELO name being a seperate entity.

or am I making a complete pigs ear of this? This is the first system I have setup (and have had great results and a lot of fun getting it working, well done Endian!) so am not a pro by any means.

Any and all suggestions welcome!