We have a couple of users who frequently hit the road, in and out of Australia.

For email access they use a direct connection to our office Groupwise system IMAP (with TLS) and SMTP (with TLS). This has been working fine for most users. But from some remote networks (internet hotspots, hotels, etc) their SMTP connections are blocked and the error mentions spamhaus which is one the RBL's that are configured on the GWIA. This error has been double checked at the command prompt with telnet.

I have since read that the spamhaus RBL typically lists all dynamically assigned IP address ranges globally, which could explain this issue.

Is there a way around this? One idea I have is to enable some sort of SMTP authentication to occur before the RBL check. What is the best fix?