I’ve been seeing email from mx#.sjc.ebay.com but my DNS hasn’t been finding them. I’m also seeing mxpool#.ebay.com as well.
In order to get the actual mails, I’ve had to lie to PostFix about the existence of those addresses by sticking a list like this into a flat file and PostMapping it:
...then adding that file to a...
check_helo_access regexp:/etc/postfix/filename...statement in “/etc/postfix/main.cf”.
If I wasn’t managing my own email domains, I wouldn’t have this option.
I’m also not about to turn HELO domain checking off, because I’m not interested in about tripling the number of spam messages my filters see (already at about 1,000 a day).