[exim] Deliver at once, no queue behavior - is it possible?

Hello!

I have a HA (active-passive) firewall setup. Till now The SMTP traffic was forwarded on the TCP level to the internal mail server. But I'd like to check the SMTP traffic on the firewall too. I can configure the Exim to check the recipients, check for viruses, SPAMs etc., the usual stuff.

My problem is that I want to deliver the incoming messages at once to the internal mail server and send OK to the sender server only AFTER the internal server accepts the message. This way I can solve the what happens if the firewall crashes after it receives the message but before it delivered to the internal mail server question. If the firewall crashes the sender will timeout and will try to deliver the e-mail again later. The worst case scenario is that the e-mail arrives twice which is better than losing it.

Is this possible with Exim? I'm using CentOS 7 with Exim 4.84.

Thanks for any help/suggestion.

Árpád Kunszt

PS: Sorry for my English, it isn't my mother language.