Deliver a mail to multiple lmtp backends

[Reinhard Vicinus]

Hi,

i'm in the process of replacing the lmtp backend of our mailservers. For 
testing the new lmtp backend i would like to deliver mails for selected 
users to both, the new and the old lmtp backend.

In the past i have made a similar transition but with exim as mta. With 
exim this is very easily done with the unseen option (delivery of a mail 
is stopped, as soon as a message is "seen", unseen marked transports, 
don't mark a message as seen so other transports are also trickered), 
but i can't find how to configure postfix to do the same.

Thanks,
Reinhard