Kerio Connect reports all rejected emails and connections to the security log. If Kerio Connect is rejecting a message from a legitimate address, it will be reported in this log. You can search this log by using the Find search bar in the window.

Perform an upward search from the bottom of the log for the sender's email address. The matched result will tell you the particular blacklist where this user's outgoing mail server was listed.

Once you have identified the blacklist, you will need to change its action:

1. From the Administration Console, go to Configuration > Content Filter > Spam Filter.

2. Under the Blacklists tab, edit the appropriate blacklist and change the action from 'Block the message' to 'Add spam score to the message.'

3. Assign it a value of 10, which will ensure that any message from senders in this blacklist will be marked as spam, and can be filtered accordingly.

Now that these messages are going to be received by Kerio Connect, they can be processed by the spam filters, which will allow you to make exceptions based on header information.

Spam filter rules are defined in the Spam Rating tab under Configuration > Content Filter > Spam Filter > Custom Rules tab.

1. Create a new rule (Example: whitelist email address) where the message header 'From' contains the email address of the sender who is being rejected by the blacklist.

2. Choose to 'Treat the message as non-spam.'