Hello @CDres ,
When you upload a contact list, the system checks for new information in already present contact fields. So if you upload a list with a contact (email address) that has a value in the first name column different from its current first name value, then the newer one will be reflected after the upload is complete. If a field is blank or not included in the reupload, then the existing info will not be overwritten in the reupload.
Based on your description, it sounds like you may also be wondering if uploading a file to an already existing list will erase any contacts not included in the reupload? If that's what you mean, then no, uploading lists doesn't overwrite contacts not included in those lists. If you're needing to update a certain list's membership to no longer include contacts that aren't part of your upload, then you'll need to consider whether you're:
- wanting the contacts not on the list to absolutely not be among your active contacts, or
- simply remove the unincluded contacts from the list, but otherwise keep them among your active contacts.
In situation A, you're going to want to go into the list you'll be reuploading to, select-all the contacts, and delete them. When you perform the reupload with the updated contact file, our system will restore information for those deleted contacts that are being re-added, and update any different contact fields as necessary.
In situation B, I'd advise simply deleting the list only, which will keep all those contacts in your account, but otherwise unbind them from that one particular list. Then reupload your updated contact file as normal, and recreate the list on the list selection step of the upload.
If you need clarifications or elaborations on either of these, just let us know here in the thread or the automated @ mention email, and we'll see if we can break down the process further.
Formatting contact files for upload
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