WithWine keeps one customer record for each email address. When you import a CSV file that includes customers who are already in WithWine, WithWine matches them by email address and merges the new details into their existing record. It doesn't create a duplicate customer.
What gets merged
Most details are added to the customer's record, without removing what's already there:
Tags: new tags are added to the customer's existing tags. For example, if one import gives a customer the tag Long lunch 2026 and a later import gives them VIP, the customer has both tags.
Addresses and names: if an import has a different address, or a different first name and last name, WithWine adds a new contact card for the customer. The existing contact card stays.
What gets overwritten
Details that can only have one value are replaced by the value in the latest import. For example, Is Mailing List Subscriber can only be yes or no. If one import sets a customer to YES and a later import sets them to NO, the customer ends up as NO, and is no longer on your mailing list.
Watch out for duplicate email addresses in one file
If the same email address appears more than once in a CSV file, WithWine processes each row in turn, so a later row can overwrite an earlier one. For example, if a customer appears in row 20 with Is Mailing List Subscriber set to YES and again in row 120 set to NO, the customer ends up as NO.
Before you import, check your CSV file for duplicate email addresses and remove or merge them. In Excel, you can use Data > Remove Duplicates on the email column.
Why WithWine merges
Merging means you can safely import more than one list, such as an old mailing list and a list from an event, without losing tags, addresses or history from earlier imports.