I have query related to mail flow for incoming mails from external domains from Internet facing site. There are two sites - Site A & Site B. Both have Exchange 2013 CAS servers in NLB and Exchange 2013 Mailbox in individual DAG - say DAG1 in Site A and DAG2 in Site B. Site A is Internet facing site and site B is not Internet facing.
An incoming Internet mail meant for recipient in Site B will land in Exchange 2013 CAS server in Site A. This CAS Server in Site A will look for the recipient in local Domain Controller and get to know the mailbox database of this recipient is in DAG2 ( in site B ) Will the FET service in EX2013 CAS in Site A make a SMTP connection with FET service of EX2013 CAS in site B which will then make SMTP connection to EX2013 Mailbox server in Site B which is holding the recipient mailbox Active copy for delivery.
OR
EX2013 CAS will send this mail to Ex2013 Mailbox server in site A and the Hub Transport service running in in site A will then make SMTP connection with EX2013 Mailbox server in Site B which is holding the recipient mailbox Active copy
Need clarification on above
Thanks
Parveen