Deliverability
Updated
Email warmup
Definition
Email warmup is the practice of gradually increasing sending volume from a new domain or IP address so mailbox providers can build a positive reputation for it before you send at full volume.
How it works
Mailbox providers have no history for a new domain or a new dedicated IP. Large sudden volume from an unknown source looks like spam, so it gets deferred, rate limited or filtered.
Warmup starts with small daily volumes sent to your most engaged recipients, then increases step by step while bounce, complaint and deferral rates stay low.
On shared IP pools, the IPs are already warm and the main thing to build is your domain's reputation. On a dedicated IP, you are responsible for warming the IP too.
Example
Slow down whenever deferrals or complaints rise.
Why it matters
Skipping warmup on a new domain or dedicated IP often means deferrals, bounces and spam-folder placement on the first large send, which damages reputation from day one.
A proper warmup gives every later send a better starting point.
Best practices
- Start with recipients who opened or clicked recently. Their engagement is what builds reputation.
- Increase volume gradually and keep a consistent schedule instead of occasional large blasts.
- Authenticate the domain fully (SPF, DKIM, DMARC) before the first send.
- Pause the ramp when deferrals, bounces or complaints rise.
- Avoid automated warmup networks that exchange fake opens and replies. They create artificial engagement rather than reputation with your real audience.
How Lumail handles email warmup
Lumail sends through Amazon SES. On shared sending, the infrastructure is already warm, so you build your own domain's reputation by starting with engaged subscribers and sending consistently.
If you use a dedicated IP, Lumail shows its warmup status and alerts you when warmup has not started or appears stalled. Test sends to yourself do not warm an IP. Only real campaign and workflow volume does.
Check a real message with the free mail tester or the spam tester.
Frequently asked questions
How long does email warmup take?
Commonly two to six weeks, depending on target volume and how engaged your recipients are. Let your metrics, not the calendar, decide when to increase.
Do I need to warm up a new domain on a shared IP?
Yes, more gently. The IPs are warm, but mailbox providers increasingly judge reputation by domain, and a new domain has none.
Are automated warmup tools safe?
Tools that send to networks of inboxes and auto-open or reply create engagement that does not come from your real audience. Real, gradual sending to engaged subscribers is the reliable approach.
Related terms, tools and docs
- DeliverabilitySender reputationSender reputation is the trust score mailbox providers assign to your sending domain and IP addresses, based on how recipients and their systems react to your mail.
- DeliverabilitySoft bounceA soft bounce is a temporary delivery failure: the receiving server deferred the email but the address may accept it later.
- DeliverabilityEmail deliverabilityEmail deliverability is the ability of your emails to reach recipients' inboxes rather than bouncing or landing in spam.
- List managementList hygieneList hygiene is the routine of removing or suppressing email addresses that hurt deliverability: hard bounces, spam complainers, long-inactive subscribers, invalid addresses and likely spam traps..
- Free toolFree mail testerSend a real email and get an SPF, DKIM, DMARC and content report.
- Free toolFree spam testerCheck an email for the patterns that push mail to spam.
- DocsDedicated IP warmupWhat to do when warmup is not ready or stalled.
- DocsAccount verificationHow sending unlocks when your domain verifies.
- DocsSender healthHow Lumail measures sending health and authentication.
Browse every definition in the email marketing glossary.
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