SMSMSE spam mail forwarded from trusted domain

Hi,

We have Microsoft Exchange 2013 SP1 with SMSMSE for one domain (domain A), and Kerio Connect (a 3rd party mail server) for another 3 domains we managed. (domain X, Y, and Z)

For some reason, we'd like to forward all mails from domain Z (Kerio) to domain A (Exchange 2013, SMSMSE). However, some users in domain Z suffer from spam issues. If we forward all emails, will SMSMSE lower the reputation on domain Z, or even report it to Symantec causing it to be marked as a spammer? If so, how do we prevent it?

ps. Will the internal spam filter on Microsoft Exchange 2013 do the same thing?

Thanks,

-Andrew