Wordpress Hosting

We have dedicated servers too but it only takes one of your clients with a pc that has a virus or spyware and it can easily then send out unsolicited email so being on a dedicated server with "nice" clients means nothing unless you have taken steps to implement greylisting, spamassassin, rbl etc

Fair point. All I would add is that (generally) the problem comes from 'not nice' clients sending out such campaigns directly rather than the route you have suggested. And such clients usually choose cheap hosting packages !!!

Can I ask what 'rbl' is?

RBL stands for Realtime Blackhole List, this is a term for DNS based systems designed to assist in the prevention of email abuse. The first such system was created by Mail Abuse Prevention System (MAPS) LLC who have been granted a Service Mark for the term. The generic name for wsuch services is DNSBL.

The DNSBL consists of a DNS based system containing lists of IP addresses whose owners refuse to stop the proliferation of spam whether this be by running their mail servers as open relays, or by allowing their dialup users free outbound access to port 25.

As subscribers to the DNSBL, ISPs and companies will know from which IP addresses to block traffic. Most traffic blocking occurs during the SMTP connection phase. The receiving end will check the DNSBL for the connecting IP address. If the IP address matches one on the list, then the connection gets dropped before accepting any traffic from the spammer.

Some ISPs, though, will choose to blackhole (or disallow) IP packets at their routers. The goal here is to block all IP traffic.


On your mail setup, you should be checking RBLs against the sending IP