MxToolbox - test your external email servers
Email Server Test - Online SMTP diagnostics tool - MxToolbox
Do you want to know if you have properly configured your external mail server to not be an open relay for spambots? Do you want to see if your mail server is blacklisted on various spam sites? MxToolbox is a free site that allows you to test your mail server for a variety of issues and has a simple interface to take steps to fix any problems that might be found. There are many sites that want you to pay a fee for these tests but I have found MxToolbox to be great and highly accurate.
Yesterday I ran into a problem where an external mail server got blacklisted due to a spambot infection on a machine on our network that was NAT'ing through the same IP address of our mail server. I had the machine pulled off the network within a few minutes of seeing the problem but at that point the damage was already done to our reputation and we started getting NDR's from various servers due to our blacklisting. MxToolbox allowed me to see who had blacklisted us and start the removal process all from one spot. This saved a lot of time and effort on our part instead of having to guess which list was blocking us.
Another good tip from yesterday is to block SMTP traffic flowing from your network except from your Edge Transport server. This will stop any spambot from originating on your network and not cause these types of issues. I was able to see who the culprit was by looking at all active connections on our firewall to port 25 of an outside address. I now have a firewall rule set up to block these types of connections in the future.
Do you want to know if you have properly configured your external mail server to not be an open relay for spambots? Do you want to see if your mail server is blacklisted on various spam sites? MxToolbox is a free site that allows you to test your mail server for a variety of issues and has a simple interface to take steps to fix any problems that might be found. There are many sites that want you to pay a fee for these tests but I have found MxToolbox to be great and highly accurate.
Yesterday I ran into a problem where an external mail server got blacklisted due to a spambot infection on a machine on our network that was NAT'ing through the same IP address of our mail server. I had the machine pulled off the network within a few minutes of seeing the problem but at that point the damage was already done to our reputation and we started getting NDR's from various servers due to our blacklisting. MxToolbox allowed me to see who had blacklisted us and start the removal process all from one spot. This saved a lot of time and effort on our part instead of having to guess which list was blocking us.
Another good tip from yesterday is to block SMTP traffic flowing from your network except from your Edge Transport server. This will stop any spambot from originating on your network and not cause these types of issues. I was able to see who the culprit was by looking at all active connections on our firewall to port 25 of an outside address. I now have a firewall rule set up to block these types of connections in the future.
posted by Rick Mitchell Solutions @ 12:01 PM
2 Comments:
At December 23, 2009 9:11 AM ,
MxToolBox Support said...
Thanks so much for recommending our DNS tools! We are working hard on creating an all in one tool that does all the DNS test and lookups you could ever need! If you have any other tools additions or feedback, please let us know.
At December 27, 2009 7:38 PM ,
Rick Mitchell Solutions said...
No problem - you have created some great tools that are a big help to any mail administrator!
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