IP warmup

IP warmup is the practice of gradually increasing the daily sending volume on a brand-new sending IP — instead of sending the full target volume on day one. Mailbox providers (Gmail, Outlook, Yahoo, regional providers) score IPs partly on sending history; an IP with no history is treated with suspicion, and a sudden burst of high-volume mail from such an IP looks indistinguishable from a spam-cannon takeover. Ramping volume linearly or exponentially over 4-6 weeks gives the IP time to accumulate positive engagement signals (opens, clicks, low complaints) before it is asked to handle full production load.

AcelleMail v4.2 introduced a first-class warmup module. The model app/Model/WarmupStrategy.php defines the strategy taxonomy with constants:

• Status: STATUS_INACTIVE · STATUS_ACTIVE
• Limit type: LIMIT_TYPE_PER_DAY_CAP · LIMIT_TYPE_TARGET_VOLUME · LIMIT_TYPE_STOP_AFTER_DAYS
• Growth strategy: GROWTH_STRATEGY_LINEAR · GROWTH_STRATEGY_EXPONENTIAL
• Presets: PRESET_BALANCED · PRESET_CAUTIOUS

Daily usage is tracked in SendingServerWarmupUsage; per-day execution lives in SendingServerWarmupLog; and the cron-friendly command app/Console/Commands/WarmupListServers.php applies the strategy to every active sending server on schedule. The strategy can be attached to any sending server — SES, Mailgun, generic SMTP — independently of the driver.

Linear growth adds the same fixed number of messages per day (50 → 100 → 150 → 200…). Exponential growth multiplies (50 → 100 → 200 → 400…) and reaches target volume faster but is more aggressive at the tail. The balanced preset uses linear growth with a moderate daily increment; cautious uses linear with a smaller increment and a longer ramp window. For brand-new domains (no historical reputation), cautious is the safer default; for an IP migration where the domain already has reputation, balanced or even exponential is acceptable.

Most ESPs publish similar 4-6 week ramp schedules. A typical cautious linear ramp targeting 50,000 messages/day:

• Days 1-3: 50 / 100 / 200
• Days 4-7: 500 / 1k / 2k / 3k
• Week 2: 5k → 10k
• Week 3: 15k → 25k
• Week 4: 30k → 40k
• Week 5: 45k → target (50k)

The exact numbers are less important than the discipline: never double yesterday's volume on the new IP until reputation is established. The full warmup playbook including how to read SES reputation feedback during ramp lives in deliverability §7.