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Segment, email aliasing and Customer.io

Right now, Customer.io doesn’t support alias calls from Segment; they implement anonymousId to identify users, and it’s not possible to connect anonymous user data with a newly created id in Customer.io.As a result, you might end up with duplicates. You might have come across this issue if:

  • You’re integrated via Segment and are changing ids.
  • You have a list of pre-signup emails that may then create accounts later on.

Why don’t you support alias calls?

We want to make sure that the people receiving messages are those who have signed up for your service; however, in some cases, we recognise that this isn’t ideal.

How this might happen is: if you send us an identify call with some attributes attached, we first look at the id associated with that call. If the id is new, a new user is created with those attributes. If that id already exists, we update only the attributes that are different compared to the previous call. We do not update or change the id. So if the id is new to Customer.io, a new (duplicate) user is created, even if you may have just wanted to update a previous one.

What can I do?

There are a couple of options here, and this depends if you’re concerned about duplicates of existing users, or if these customers are new ones that haven’t yet signed up.

For existing users

In the cases of existing duplicates, we use the following process:

  1. Export a CSV of your customers from the People page by clicking on the Export to CSV button.
  2. Identify the duplicates. We recommend keeping the first instance of each— the one with an older created_at timestamp.
  3. Create a new CSV file with all of the user ids to delete.
  4. Delete those users with our API.

New users

If these are new users, however, the process is a little more complex. We have a couple options here:

  1. Do not call identify until the user signs up for an account.
  2. Filter identify calls so that they’re not sent to Customer.io (you can do this by using selective integrations).

As always, if you need any help with this process or have any questions, please let us know!