Hi @ISOOSI
Good questions. I think clarifications would help on a customer “subscribes to an email list” and “adding to cart” as I think they’re confusing the issue a bit.
When a contact subscribes to a list, they are giving their permission for you to send them marketing emails. It also means that Klaviyo can identify them by their email, and it sets a 2-year ‘identifying’ cookie (7-days for Safari) on their device; you will now see the various events they trigger captured in their Klaviyo profile (including checkout-started).
‘Add-to-cart’ is an event before checkout. Unless you take additional steps to configure this, there isn’t one in the standard configuration. More info on that here for Shopify; https://help.klaviyo.com/hc/en-us/articles/115001396711. That event also needs the identifying cookie to be set for it to trigger.
So, in your first scenario (new contact), you are correct: if no email is entered at checkout, the identifying cookie is not set and there won’t be a checkout-started event, so they won’t trigger your flow.
In your second scenario, for an existing Klaviyo profile, an email address must also be entered for a checkout-started event to trigger. As with your first scenario, adding the email address signifies an explicit checkout started. There are occasions when the email has to be entered manually by the contact, or it may be autofilled. The result is the same: no email, no checkout started event, no abandoned cart flow trigger!
Does that answer your questions?
Regards
Andy