Far and away, the most common delivery issue for Monday and Tuesday has been bouncebacks due to the SORBS blacklist. Based on the reports we’ve gotten so far this week, the latest SORBS dynamic IP listing update has included a great number of static IP’s by mistake, resulting in many legitimate email messages being blocked by SORBS users.

We’ve also noticed a trend of bouncebacks coming from IP addresses showing CBL as the operative blacklist. In a great many of these cases, the CBL site has listed the Bagle worm as the cause of the virus that’s causing spam to be broadcast from multiple networks.

In other scenarios, reverse DNS issues (PTR records not pointing to the original IP address or missing “A” records) have been found, along with a few instances of domain names being spoofed. We’ll keep you posted.