Welcome- and thanks for posting! :)
At the moment, while you can't bulk email customers through your Shopify admin, the best way to do this would be with an app such as Mailchimp like you suggest.
These apps usually work by syncing with the data from the customer section of your admin.
You can find some great options within our app store under 'email marketing'.
We also have a handy guide here which you may find useful for reference too.
I hope this helps!
Koreen W | Shopify
I just found this, which seems like it has an option to do what you want. (I was looking for the same functionality).
I'll let you know how it goes after I install it.
Confirming this app works:
You need to make sure that it is configured correctly or else you may end up sending repeated messages to customers. Their support was great and provided me this best practice for that configuration:
Let's say you want to configure a notifier, so that it will only send 1 email to the customers whose orders are unfulfilled for 15 days, Please follow the below steps.
1. Configure include-exclude of unfulfilled orders range to 15-16 (1 day gap)
2. Set reply-to and bcc field. reply-to field will let customers reply to the email to mention email address And bcc field will let you have a copy of the email that your customers are receiving.
3. Set frequency to run the notifier every day
4. click on the save button.
That's it. It should do the rest of the job.
How does this work?
- Notifier will be triggered as per frequency setup (once every day as per above setup). It will find all the order unfulfilled under 15-16 days. This way every order unfulfilled for more than 15 days will be caught only once by the notifier and email will be sent to the customers of orders 1x at the 15 day marker.