SMTP Relay in Active Directory Site

Environment:

Exchange 2010 + 2013 coexistence. The SMTP send connector includes 4 Exchange 2013 servers located in 2 AD sites (site A and site B).

Issue:

2 Exchange servers in site B in the SMTP send connector are down. However, other Exchange servers located in site B still keep relaying emails to them through SMTP Relay in AD Site.

Question:

Should other Exchange servers be aware that these 2 Exchange servers are down, and stop relaying emails to them? How to fix this?

Thanks,

Kevin