Email threading
Follow-up steps in a sequence land as replies in the same conversation as step 1, not as separate, disconnected emails.
Why threading matters for cold email
A follow-up that shows up as its own new email, with its own subject, reads as spam-adjacent and easy to ignore. A follow-up that shows up as a reply in the same thread — "Re: Quick question about Acme" — reads like a real, ongoing conversation, and is what every inbox provider's own UI groups together automatically.
How it's implemented
Two things make a message thread correctly in a mail client:
- Subject reuse — every step after the first automatically reuses step 1's subject with a
Re:prefix (see Steps & sequences) - Real threading headers — each follow-up is sent with proper
In-Reply-ToandReferencesheaders pointing back at the previous message in the sequence, exactly like a real reply would carry
This is tracked per contact automatically — there's nothing to configure. It's also part of what makes stop-on-reply and inbox-side reply detection reliable: a genuine reply from the contact lands in the same thread SubsiMail is already watching.
