Use of fallback relay

[maxxer]

Hi.

I've an installation where I'm configuring direct delivery from Zimbra, but would like to mantain the current relay as a fallback.

Is it possible?
Should I use fallback_relay postfix config option, or is there any specific Zimbra config?
thanks

[MobiusNZ]

its not generally recommended to use a fallback relay anymore, as it adds to spam woes. RFCs dictate that a mailserver should keep retrying to send mail for 4-48 hours anyway...

[maxxer]

I understand, but it seems I cannot set rDNS on the line, and I know that some mailserver reject mails if the ip is not resolved correctly... so I'm forced to do so