Email Warmup
Also known as: Domain Warmup, Inbox Warmup
Email warmup is the practice of gradually increasing send volume from a new domain or mailbox while generating positive engagement (opens, replies, removing-from-spam) to build sender reputation with major mail providers. Warmup typically takes 4 to 8 weeks to bring a domain from zero to a few hundred messages per day in good inbox placement.
A brand-new domain has no reputation. Gmail and Microsoft default to suspicion. send 200 cold emails from a fresh `outreach@newdomain.com` on day one and most of them land in spam. Warmup solves this by ramping volume slowly while every message gets opened, replied to, and marked-as-not-spam by other warmup participants.
How warmup tools work
Services like MailReach, Warmup Inbox, Lemwarm, Instantly, and Smartlead exchange real conversational emails between participating inboxes. Each day the tool sends a slightly larger number of emails, with each message getting an open and a one-line reply from a peer mailbox. The receiver sees consistent low-volume engaged sending that looks like a normal human user.
How long warmup takes
Four to six weeks is the realistic minimum for a new domain. Eight weeks to comfortable sending volume. The first two weeks are the slowest. ten to thirty messages per day. The ramp accelerates from there but should never jump more than 30 to 40 percent week-over-week without observing inbox placement.
When warmup is required
- Brand-new sending domains
- New `outreach@` mailboxes on otherwise-warm domains
- Resuming sending after a 60+ day pause
- Recovering from a deliverability drop after a content or volume mistake
Warmup is not required for the marketing domain that already sends millions of newsletter messages per month, unless reputation has degraded.
Frequently asked questions
Can Outsolvi do warmup?+
No. Outsolvi is the tracking layer, not a sending platform. Warmup runs on the sending side (your cold-outbound tool, or a dedicated warmup service like MailReach).
Is warmup-pool engagement detectable by Google?+
Increasingly, yes. Modern warmup providers obfuscate patterns but Google and Microsoft have become better at detecting reciprocal warmup networks. The defensive move is to send genuinely engaging mail to real prospects as soon as the warmup ramp permits, so the engagement signal is real and not warmup-pool synthetic.
Put this concept into practice
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Related glossary terms
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We update these pages when the underlying mechanics change. new mailbox-provider rules, new tracker behavior, new measurement gaps. The dates above are real revisions, not auto-touches.