This feature is available in PoliteMail version 4.956+
When sending to a distribution list, a user may get this warning after clicking Send on a tracked message or get recipient count.
This warning appears only if the distribution list is successfully expanded, but the contact count came back as zero. Either the distribution list is empty, or the list has hidden members. PoliteMail is unable to determine whether or not the list actually has zero members, or if those lists have hidden members. PoliteMail will only send one copy per recipient, however, the list is considered a recipient, thus any contact who is in that list will receive another copy of the message (thus skewing the metrics).
If the user receives this warning, they can choose to save their message and then go back to their distribution lists and make sure there are no empty ones, especially in a nested list.
Or, if the user wants to send the message, they can choose "Always switch to Aggregate mode on empty lists." This will count device Opens, and treat what is considered an empty list as one contact.
Ignoring the message by clicking OK will send the message as expected. For example, if you're attempting to send your message with Individual tracking, it will send, but will not provide accurate counts for contacts in those lists that have been marked as hidden or empty. Again, it will only count these lists as 1 contact.
The user could also choose to check the "Don't show this message again" box. In this case, the user will not be prompted if there is a possibility of an empty list it will behave as described above depending on your tracking method.
If you wish to turn warnings back on, go to PoliteMail > Preferences. Click on Re-establish List Warnings.
For more information about fallback list expansion methods, please click here.