The consolidate feature of the mail list allows two or more entries exist in your mail list for the same customer to be amalgamated into a single entry. You could simply remove one of them, however this has the undesirable effect of removing any customer history relating to the lost entry. Ideally you would want to remove one of the entries and transfer the associated history to the remaining one. This is precisely what the consolidate feature does.
In order to consolidate entries you will first need to know the customer references of both of the entries in your mail list (the Identify Duplicates tool is useful for gathering information for this). The next step is to decide which of the entries you wish to keep, find it in the mail list and click on it so that it is highlighted. Once highlighted click the Consolidate button and the following window will be shown.
Next enter the customer reference for the entry you want to remove and then click the OK button. You should have something link the image shown below, which details both of the mail list entries and asking for confirmation of the deletion.
Click Yes to confirm the removal of the unwanted entry or No to abort the process. To prevent to accidental removal of customer information it is not possible to consolidate two entries which do not have the same surname.