Product
One mail plane. Send, receive, automate.
Mailstack is the whole stack a product needs to run on email — not an API bolted to someone else's inbox.
Send
Templates, not string-building
Substitution-only templates an operator edits in a browser. A missing variable is a refused send, not a blank in a real person's inbox.
Authentication that passes
SPF, DKIM and DMARC aligned on your domain, with one-click unsubscribe attached wherever it's required.
It stops itself
A campaign that crosses a bounce threshold blocks and asks a human, instead of finishing the list and burning the domain.
Receive
Threads and attachments
Real IMAP-backed receiving, cross-folder search, and replies matched to the message that provoked them by Message-ID.
A reply pipeline
Opt-outs, yes, no, bounce and human — classified and acted on, so an unsubscribe becomes a suppression without a person in the loop.
Automate
Campaigns with planes
Paced, resumable sending whose position is state — a daily run with a rising cap is the whole warm-up — and which cannot send from a transactional domain.
A scheduler you can see
Cron jobs as rows you add, pause and inspect from the console. The last run and its error are where you'd look for them.
An agent surface
One account-scoped key over the same functions the console uses — never a way around the gates, always a caller of them.