Why Can’t Someone Send to My Exchange Account?

Once in awhile you may find that someone calls and tells you that they sent you email, but that it got returned to them for no apparent reason. We all know that we have to be careful about adding specific words to our email, or sending out too much email to the same person, in order to not look like we are “spamming” them, but sometimes it is not all that obvious when one of our simple messages gets returned for no apparent reason.

Hidden Factors: When this happens there can be “hidden” factors involved that are in play. Often the person sending the message is not at fault, but instead the organization they are working for may have some issue, such as a computer on their network that has been compromised with a virus and is sending out thousands of spam messages. These spam messages often pass through the same network gateway (shared IP address), which make everyone on that network look as if they are sending spam also. This is called having a “poor IP reputation”.

Barracuda Reputation: Many organizations like ours use active spam filter appliances, that perform multiple tests against each incoming email, and reject some messages outright if they fail one of the tests. Most notably, each incoming message has its sending IP address tested against a central list of known IP addresses with “poor reputations” for previously or currently sending spam. The same type of lists exist for domain names that have poor reputations. If someone sending you email has a shared IP address or shared domain name that is on a reputation list somewhere, their message to you will likely be returned as undeliverable.

What To Do: Unfortunately, our Barracuda filter treats some spam conditions like “poor IP reputation” as very serious, and simply returns the message to the sender without notifying you that the message was denied. Even if you set up a Barracuda quarantine box, and set your spam capture score very low, this type of message will never end up in your quarantine box. They are simply rejected outright by Barracuda. If you discover that this has happened,  you need to do one of the following.

1. Ask the sender to resend the message again, but this time have them send it to a personal email account, such as your Yahoo or Gmail account to ensure their email is actually able to send mail to someplace other than your Exchange account.

2. Have the sender check the return message they got to see if there is an explanation as to why the message was returned (ask them to check for the words, virus, IP reputation, RBL or blacklist, etc.). If they find any of these indicators, they need to check with their own network administrators for help getting their shared IP address off of any blacklists.

3. Consider placing the sender’s full email address in your private “white list” found under your Barracuda quarantine setup at http://go.middlebury.edu/spam . If you have not already set up your quarantine box on the Barracuda, you may want to take a few minutes to do so. Instructions for adding to your white list can be found at http://tinyurl.com/middspam .

Additional Help: You may search for more information on the above subject, by typing “IP reputation” or “barracuda spam list” into your web browser search field. For further assistance setting up your Barracuda quarantine box please contact the ITS Help Desk at x6656 or at HelpDesk-MIIS.