We've been running the greylisting package for about a year and it's helped with our spam problem wonderfully. However, I'm seeing a trend of companies moving towards cloud based services that are using more of a round robin style of mail server (Eigbox.net hosted services & more recently Office365) which are generating "client_name=mail-by2on0128.outbound.protection.outlook.com" and "client_name=mail-bn1on0138.outbound.protection.outlook.com" entries, each with a new IP address for clients who have emailed me for years, causing delays of upwards of 30-45 minutes. The "Eigbox.net" swarm is even worse at 60-90 minutes.

I've tried adding the domain to the whitelist, but when the client_name keeps changing dynamically (First message: sender=SRS0=eGL_H0=Q4=CLIENT-DOMAIN.net=CLIENT@eigbox.net ----- Second Message: sender=SRS0=Dp956B=Q6=CLIENT-DOMAIN.net=CLIENT@eigbox.net), it seems that the greylist is becoming more of a burden. I've tried whitelisting the client domain, as well as eigbox.net.

Now, knowing that there's nothing I can do about the client retry time, I'm looking to see if anyone else has had issues like this which they've overcome.