We are running Exchange 2013 with multiple accepted domains.
We are stuck with some external recipients reporting that mails sent from 'Domain B' are going to SPAM folder with the reason as "sender not validated'
We have single send connector with HELO response FQDN set as the primary default domain (Domain A)and all other accepted domain mails using the same connector for sending mail. We are using a wildcard certificate as *.domainA.com.
One option may be to define another send connector with Smart host and HELO responce FQDN as that of Domain B so that emails sent from Domain B users, take a different route with different source address and reach gracefully.
Is their a better way doing this without involving Smart host