I am running a postfix server and now I would like to know if I can configure postfix to deliver mail to a virtual domain locally and also forward it to a second remote mta. The problem is that both mta handle the same virtual domains so virtual_alias_maps, bcc or anything other address/domain related will not work. If this setup is not possible with postfix, is there another mta (maybe exim?) that is capable of doing this?
Beside configuring Postfix on a secondary MX (http://www.postfix.org/STANDARD_CONFIGURATION_README.html#backup) it is not possible. And even then it is not capable to deliver a mail to more than one destination MTA. It can only be delivered to one or another destination, but not to both at the same time.
Your request is not specified in the SMTP RFC 5321. It isn't specified because it would require a two phase commit to finally deliver a mail to two destinations. Which answer should a sender receive in case of one MTA failing and one MTA succeeding?!