Warm-up
How Zylar warms inboxes through a private pool of real inboxes on a ramp schedule, why it's free on every plan, and why warm-up never counts toward your sends.
Warm-up builds a sending reputation for new inboxes and protects it for existing ones. In Zylar, warm-up is on by default: it starts the moment you connect an inbox, runs through a private pool of real inboxes and ramps on a schedule. It's free on every plan and never counts toward your monthly sends.
How warm-up works
Mailbox providers trust inboxes that send consistently and get engagement. A brand-new inbox has no history, so sending cold email from it straight away looks like spam.
Zylar's warm-up sends email between your inbox and a private pool of real inboxes. Those inboxes generate the signals providers look for:
- Opens
- Replies
- "Not spam" marks, moving the message out of spam if it lands there
These happen on a ramp schedule, so volume increases gradually instead of jumping.
The ramp
Warm-up starts when you connect an inbox and ramps until the inbox is ready for cold sends. How long depends on the inbox type: about 10–14 days for Outlook tenants (3–7 days minimum), 15–25 days for Google Workspace and 4–6 weeks for private SMTP. While it ramps, the inbox's status is warming. Plan your launch around that window: connect inboxes well before the campaign date, especially Google and SMTP inboxes.
Daily limits work the same way. You set a daily limit per inbox, and Zylar raises it gradually rather than all at once. See Sending and rotation.
For the reasoning behind ramp schedules and how long to warm, read the email warm-up guide.
Warm-up keeps running
Warm-up isn't only for new inboxes. Zylar also uses it to recover inboxes and domains whose health drops:
- Inboxes: When an inbox's daily health score drops, Zylar switches it to warm-up only (status
resting) and moves its sends to healthy inboxes. - Domains: When a domain's placement drops below your threshold, Zylar auto-pauses it, moves its volume to healthy domains and puts it back on warm-up until it recovers.
See Monitoring and auto-pause.
Cost and send limits
| Question | Answer |
|---|---|
| Does warm-up cost extra? | No. Warm-up is free on every plan. |
| Do warm-up emails count toward my monthly email allowance? | No. Warm-up never counts toward sends. |
| Do I need to configure it? | No. It starts on connect and runs on its own. |
| Is the pool shared with the public? | No. It's a private pool of real inboxes. |
Your plan's monthly allowance is for campaign email only. See Plans and billing.
Checking warm-up status
Each inbox has a status and a daily health score from 0 to 100:
| Status | Meaning |
|---|---|
warming | The inbox is on warm-up. |
active | The inbox is in rotation and sending campaign email. |
resting | The inbox's health dropped, so it's on warm-up only and its sends have moved to healthy inboxes. |
You can also read status, health score and daily limit for every inbox through the API with GET /inboxes. See the API reference.
Good practice while you warm
- Finish DNS setup first. Warm-up on a domain with failing SPF, DKIM or DMARC builds reputation on a weak base. See Connect a domain.
- Connect inboxes in advance of your campaign, not on launch day.
- Keep enough inboxes that each one sends a modest daily volume. See How many inboxes do you need?.