Is there any way to configure reverse MX check for Postfix to check incoming emails?
I just noticed that most of our spam which are still coming true are sent (or seems to be sent) from properly configured SMTP servers, (like yahoo's or which ever), passing reverse DNS, SPF and other checks, but actually there is often no MX records in those domain names of sender addresses at all. Then when those spam mails often goes to the removed mail boxes too, our postfix tries to send notices to the senders email addresses about that, but those notices can't be send as the MX record is actually missing from the domain names of the senders email addresses.
Smart! That could be the way how I would send my one time mass spams, as I would probably not care about those notices to senders addresses and get just load to my domain (if even in use), and I could too leave my MX record to be not recorded.
However, by assuming that who will send important emails for me, he would use senders email address which can actually receive my reply too, and would therefore have MX record in the domain name of his senders address too. So, I could just reject those incoming emails which are send from the senders addresses which does not have MX records. Right? But how could I do that? Any advice for this?