How warmup works

Warmup builds sender reputation the way reputation is actually earned: by sending real mail that real mailboxes open, read, and reply to. Here is exactly what happens after you click Start Warmup.

The network

When you connect a mailbox, it joins a shared warmup network made of two pools: peer mailboxes — other users' connected mailboxes — and an operator-run seed pool. Your mailbox exchanges mail with the network in both directions: it sends warmup messages to other members, and it receives, opens, and replies to theirs. Every mailbox is both sender and audience, which is what makes the engagement signals genuine rather than simulated.

The daily schedule

Each night at midnight, the scheduler plans the next day's sends for your mailbox. The plan respects your configuration:

• Sends are spread across your working hours (default 8:00–18:00) with natural jitter, so nothing fires in mechanical intervals.
• Scheduling is timezone-aware — working hours mean your hours, not the server's.
• Non-working days are skipped entirely (default Mon–Fri; you can enable 7-day sending).

The result is a send pattern that looks like a person at a desk, because mailbox providers score patterns as much as volume.

The content

Message content is AI-generated fresh for each thread, steered by your industry tags so conversations sound like your actual line of work. If generation is unavailable, a template library serves as fallback. No two threads recycle the same canned text.

Every warmup message carries a hidden X-EW-ID header. That tag is how receiving mailboxes in the network recognize warmup mail and handle it — it's invisible in normal mail clients and never appears in your subject lines or body copy.

The engagement loop

Recipient mailboxes poll their inbox via IMAP roughly every 10 minutes. When one finds a message tagged with X-EW-ID, it:

1. Opens the mail.
2. Rescues it if needed — if the message landed in spam, it's moved to the inbox. To Gmail or Microsoft, that's a user saying "this is not spam," one of the strongest positive signals that exists.
3. Replies, based on the sender's reply-rate target (default 35%). Replies continue the thread with fresh, context-aware content.

Threads cap at 4 messages, so conversations end the way human ones do — naturally, not mid-sentence and not in infinite loops. Your mailbox performs the same open/rescue/reply work for other members, which is why the IMAP connection is required, not optional.

The ramp schedule

Volume climbs gradually to your daily target. Jumping to full volume on day one is exactly the pattern spam filters are built to catch, so the ramp is enforced:

The ramp stops at your configured daily target — it never overshoots. Plan caps apply on top: Free 20/day, Starter 100/day, Pro 200/day (see pricing).

Safety cutbacks

Warmup watches your bounce rate. If it exceeds 3%, volume is automatically cut to 25% of the current level. Bounces at that rate usually mean a deliverability problem — a DNS misconfiguration, a blacklisting, a provider-side block — and continuing to send at full volume would make it worse. Fix the underlying issue (start with the SPF/DKIM/DMARC checker), and volume recovers as bounces subside.

Tuning it

Every knob mentioned here — daily target, reply rate, working hours and days, timezone, industry tags, pause/resume — is configurable per mailbox. The settings reference covers each one with defaults and guidance.