Posted December 31st, 2008 by Matt Shadbolt
If your having intermittent DSN errors returning to your users with the message “mail.someremoteserver.com #500 Firewall Error##” I’ve found the the error is actually due to your local Cisco router/firewall.
It seems that some Cisco routers and IOS versions that use the ip inspect command on the outgoing interface have problems with the newer Exchange 07 [...]
Tags: 500 Firewall Error, cisco, Exchange 2007, ip inspect
Posted October 15th, 2008 by Matt Shadbolt
Upgrading your IOS is generally a pretty strait forward task. There is one consideration you should make before attempting to upgrade your router – the required “feature set”.
If you install an IOS image that doesn’t include some of the features included in your previous IOS version you may find that some functionality is lost.
You can [...]
Tags: cisco, Cisco IOS Software, Feature Set, IOS
Posted July 30th, 2008 by Matt Shadbolt
I’ve recently had issues with my companies IP address being blacklisted by a bunch of RBL’s (Realtime Block Lists) blocking mail delivery from our server on the basis that we are sending SPAM. We of course didn’t realize there was a rouge client on our network sending bulk unsolicited emails.
After weeding out the client – [...]
Tags: acl, cisco, network security, smtp
