I have installed the Hub/CAS server in the newly created AD site (Branch AD), which consists of additional domain controller with GC and mailbox server running in the separate hardware. My default AD site consists of one domain controller, one Hub/CAS server and two mailbox servers running SCC cluster. If I send a mail to users in the default AD site via Hub sever in the branch AD, mail not get delivered to the default AD site Hub server and waiting in the queue. Error saying target host temporarily rejected the authentication SMTP Error 4.5 Please help on this Cheers, AFRAZ

Hi Afraz,Can you run below command on the server where mails getting queued up for further details, specially full error message displayed in "Last Error"?Get-Queue "ServerName" | FLAmit Tank | MVP - Exchange | MCITP:EMA MCSA:M | http://ExchangeShare.WordPress.com

Hi, Please also enable the SMTP Protocol on the receive connector on the default AD site Hub server. Then, please reproduce the issue and post the related log here. Mike