I am adding contacts from a CSV and XLS file formats and keep getting this issue. What happens is Constant Contact is adding quotation marks to all of my data in the file. As a result, my contact's email addresses are in the wrong format. I checked the different files multiple times on my end and have not seen the quotation marks. But when I upload into Constant Contact, they are added and I cannot continue to upload them. I have managed to find a work around but it makes no sense why it works. I open in google sheets, then download as a CSV from there, and like magic its working. Same file, same data, different result.