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Frequently Asked Questions

Why can't I use Smart Groups?

We rely on the timestamp field from the subscription history table; this does not exist for smart groups. Using Smart Groups would basically un-do all the benefits of an incremental sync.

I get "Your merge fields were invalid" errors

e.g. showing in the Cache Browser for a contact. This is probably because you've defined merge fields called FNAME and LNAME (correct) but you've defined them as Required.


Do not mark any merge fields as required.

The problem can arise because you don't have a name in Civi for someone who is Added to your CiviCRM group; therefore the Mailchimp update fails because the name is required by Mailchimp. It might arise in relation to fname/lname (I’d need to check) because of the way the subscribe sync works, too, so best set those not-required.

Certainly if you have any other fields required then sync will fail as CiviCRM won't be able to provide that when subscribing people.

Why make yet another Mailchimp sync extension?

At the time of writing, there are currently three other Mailchimp sync extensions.

    • most popular one. Maintained by Veda, although not very actively (last release 2017).
    • Having written the majority of this code when Mailchimp ditched v2 of their API, I'm aware of its limitations and I realised that a fresh start was required.
    • struggles with big lists and fails when data is changed at both ends between syncs; there's no true 2 way sync as you start from the assumption that either CiviCRM or Mailchimp is correct.
    • not updated since 2014.
    • Uses deprecated Mailchimp API, considered dead.
    • not updated since 2015.
    • Uses deprecated Mailchimp API, considered dead.

I needed a solution that was easier for staff to manage; experience taught me that it needed to be more robust especially around bulk updates at either end. Also, as the two systems don't match up - one's a circle and one's a square - there's always bits that get lost in translation. While these are not fun to deal with, this extension at least allows these to be inspected and understood.

Context: "I" above is Rich Lott / Artful Robot and this extension began life in November 2019.