Warmup that adjusts itself to protect your mailbox.
Sendbox warmup builds sender reputation gradually by trading real emails with real accounts, generating opens, replies, and spam-folder rescues on its own. If mailbox health starts to dip, warmup automatically throttles volume and shifts timing to protect it.
Lambda Group
Reputation built before your first campaign even launches.
Opens, replies, and spam rescues from genuine accounts, the actual signals ESPs use to size up a sender.
The moment metrics slip, volume and settings adjust automatically to heal the mailbox rather than push it further into trouble.
Set your own starting volume, daily increase, and target, adjust it whenever you like, or leave auto-throttle to manage it.
Inbox rate, spam rate, bounce rate, and reply rate, all broken out per mailbox, so you know precisely when it's ready to send.
It's real engagement doing the work, not raw volume.
Pick a starting volume, a daily increase, and a target. Before warmup even starts, Sendbox checks your DNS records (SPF, DKIM, DMARC) so nothing is quietly holding you back.
Warmup emails go out to real accounts across the network, where they get opened, replied to, and rescued out of spam, exactly the kind of signals ESPs rely on to decide whether you're trustworthy.
If bounce rates climb or more mail starts landing in spam, Sendbox automatically throttles volume and adjusts settings to bring the mailbox back to health, without you having to babysit it.
Just picked up ten new sending domains? Turn warmup on across all of them at once, and they'll build reputation in parallel while you get campaigns ready.
If a mailbox has landed in spam, warmup rebuilds trust gradually through controlled volume and genuine engagement signals.
Between campaigns, warmup keeps mailboxes active so their reputation doesn't decay from sitting idle.
Why so many warmup tools end up flagged.
Warmup that reacts, instead of just running on autopilot
Most warmup tools just blast out a fixed volume and hope for the best. Sendbox instead watches health in real time and auto-throttles the moment something looks off, adjusting volume and timing to protect the mailbox rather than letting it burn out.
Set-and-forget warmup that actually protects you
Other tools ramp volume on a fixed schedule no matter what's actually happening, so if your mailbox starts landing in spam, they just keep sending at the same rate regardless. Sendbox catches the problem and auto-throttles instead, cutting volume, shifting timing, and healing the mailbox before real damage sets in.
Real engagement, not just volume
Volume by itself doesn't build reputation. What ESPs actually weigh is engagement, opens, replies, spam-folder rescues, and Sendbox warmup generates that engagement from real accounts, building the exact signals that move you out of spam and into the inbox.
Got questions? We've got answers.
Still stuck? Talk to us →Your mailbox sends emails to real accounts inside a warmup network, and those accounts open, reply to, and rescue your emails from spam, building up the engagement signals ESPs use to judge your sender reputation. If health starts to dip, volume and settings adjust automatically to protect the mailbox.
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