If you want your email sequences to be always in a single thread, you will have to make sure that the subject line and sending account are the same for all sequences.
If the subject line is different, the email sequences will be sent out as individual emails.
Instantly sends all the follow-ups from the same sending account, unless you remove that sending account from the campaign.
The same applies to replies sent from Unibox - they will be in the same thread and automatically sent from the same sending account used in the campaign, unless you disconnect that account or manually change it when replying.
Please note, depending on the email provider RE will be added for your follow-ups.🚀
If you want to send the follow-ups in a different thread, change the subject of your steps.