It's really hard to replicate the real authority you get with primary domains, but there may be other factors at play too (e.g. human copy, previously conversational history, lower volumes etc.)
The challenge with primary, of course, is that there is a real volume limit.
We're seeing a clear need to run both types of campaign in parallel - lower volume, hyper relevant, human-in-the-loop 1:1 campaigns via primary domains; and then higher volume, still hyper relevant, automated 1:many campaigns via secondary.
Happy to chat through how these systems work together!
