Warm up every mailbox.
Before you reach out.
Your mailboxes exchange warm-up emails with a pool of opted-in utobo mailboxes and build a sending history. You see measured inbox placement, not a made-up score.
alex@example.com · Outlook
Today: 14 sent · 12 received · age 6d
sam@example.com · IMAP
Today: 20 sent · 17 received · age 12d
hello@example.com · IMAP
Today: 3 sent · 2 received · age 1d
Example data. Nothing on this page sends email.
Three steps.
Running every day.
Trade email.
Your mailbox sends and receives short warm-up emails with other opted-in utobo mailboxes.
Engage like a person.
Warm-up emails get marked read, replied to, starred and moved out of spam.
Ramp up slowly.
Start at 3 emails a day, add 2 a day, level off at 20.
Start small.
Build up every day.
Each mailbox starts at 3 warm-up emails a day and adds 2 a day, up to 20. It reaches full volume in about 10 days and keeps warming. Raise the cap to 40 on Cold outreach plans.
See where it lands.
No made-up scores.
Warm-up shows measured inbox placement for the last 7 days, with its sample size. Until there’s enough data, it says so.
Opt in per mailbox.
Pause anytime.
Turn warm-up on for each mailbox after a clear consent step. Warm-up emails use synthetic content, never your customer data.
Consent first
See exactly what warm-up does before it starts.
Your settings
Set the daily cap, reply rate and thread length.
Pause anytime
Stop and resume each mailbox in one click.
Included with Cold outreach.
No per-mailbox fee.
Before you warm up.
Which mailboxes can I warm up?
Outlook and Microsoft 365 (sign in with Microsoft), plus IMAP mailboxes from providers like Zoho or your own domain. Gmail and Google Workspace are in Google verification and coming soon.
How long does warm-up take?
A mailbox reaches full warm-up volume in about 10 days. Warm-up keeps running until you pause it.
What does warm-up do in my mailbox?
It sends and receives warm-up emails, replies to some, marks them read, stars some and moves any in spam back to the inbox. It only acts on warm-up emails, and they stay out of Unibox.
Does warm-up use my sending allowance?
No. Warm-up emails don’t count toward your monthly campaign emails or your account’s daily sending limit.
Does warm-up guarantee the inbox?
No. It builds sending history and shows you measured placement. Where mail lands also depends on your content, list and sending habits.
Warm up before you reach out.
IMAP and Outlook today, Gmail soon. An opt-in warm-up pool. Included with Cold outreach.