Warmup
When sending emails from a new domain or IP address, it's important to establish trust with mailbox providers. IP warmup is the process of gradually increasing your email send volume over time to build a positive sender reputation.
What is warmup and why is it necessary?
Mailbox providers like Gmail, Yahoo, and Outlook monitor the reputation of your sending domain and IP.
If you suddenly send high volumes from a new or cold IP, your emails may:
- Be throttled or blocked
- Land in spam folders
- Get your IP blocklisted
Warmup ensures that your sending patterns look organic, consistent, and trustworthy — resulting in better inbox placement.
How warmup works at MX18?
MX18 automatically initiates a 30-day warmup plan for:
- Every new account
- Every new sender domain added
You’ll receive periodic email updates and alerts as your warmup progresses.
How we determine warmup volume?
Our smart warmup engine adjusts your sending limits daily based on:
- Historical engagement (opens, clicks, bounces)
- ISP feedback loops
- Complaint rates
- Internal deliverability scoring models
You don’t need to calculate daily volume caps — we do it for you.
Thresholds to maintain during warmup:
To ensure steady reputation growth, keep your metrics below these thresholds:
| Metric | Recommended Threshold |
|---|---|
| Bounce Rate | Less than 2% |
| Spam Complaints | Less than 0.5% |
| Unsubscribe Rate | Less than 2% |
| Deferred Emails | Less than 5% |
These thresholds are based on average daily sends and monitored automatically.
Plan warmup per domain
Each new sending domain is warmed up individually.
Make sure to account for this when:
- Planning new campaigns
- Launching parallel brands or projects
- Scaling volumes across verified identities
Avoid skipping warmup — aggressive sending can delay inbox placement for days or weeks.
Stick to the plan
MX18's warmup algorithm is built to:
- Maximize inbox delivery
- Reduce bounce/complaint risk
- Ramp you up safely without manual intervention
We strongly recommend following the assigned plan. Manual overrides may reduce performance or trigger delays.
Need help?
Need to discuss custom warmup plans or facing delays?
- Email our deliverability team at support@mx18.com
- We’ll review your account and assist with adjustments where needed