Hello,
We have Exchange 2013/2010 environment(coexistence). 2 CAS and 2 MBX( in DAG) servers for every Exchange version. One AD site.
1. Ex 2013 CAS servers are published to the Internet. As mail flow is performed by MBX servers Internet destination mail server receives HELO/EHLO FQDN specified in MBX send connector and this name should correspond to Internet name specified in DNS for the communicating CAS server. As we have 2 CAS servers we can have a situation when EHLO FQDN does not correspond to the checked DNS server name (PTR record). How can this be avoided?
Moreover what is the mechanism how mail is directed from MBX server to one of CAS servers? MBX send connector has no option to configure proxying CAS server.
2. I would expect that MBX server holding the active database copy is responsible for delivering a mail for an external recipient to CAS server. However it seems this is not true. Are there any circumstances when mail can be pinged between EX2013 MBX servers. Additionally I suspect this behavior is the reason why mails sent from Ex2013 mailbox are multiplied and received as few copies. It is sporadic. But still the point to be caught.
Thank you for your help.