Phew! That was a little wordy. This only applies to folks using custom fields in your contact lists, as well as segments. New contacts will not be added to a segment automatically if the segment’s condition is based on a custom field. If it’s a standard field (Organization, Division, etc), the contact will be added to the segment upon creation.
After looking at this one we’ve decided not to address this issue. These two features (custom field names and auto-adding a contact to an existing segment), do not work together. The workaround is to recreate your segment after uploading contacts.
Let us know if you have any questions or concerns.