Recently proofpoint blocked mailgun IP ranges and our dedicated IPs were part of this range hence all of our clients using proofpoint were blocking emails from our dedicated IPs. This issue was identified only after our clients started complaining after 2 days when they did not receive any emails for 2 days and missed lot of important ones. This is not good since our client had to inform us about this even though their email provider blocked our IPs but there should be some way for us to identify such issue. We do have blocklist monitoring enable on our account but Proofpoint RBL is not part of the monitoring list can you please add proofpoint to the RBL check list plus if there any more such major service providers who maintains there own RBL. This will help to identify such issue in advance.