IP Warmup by ISP — Per-Receiver Ramp Strategy in AcelleMail

Why per-ISP warmup beats uniform warmup#

Receiving servers weight your reputation differently. Send 50k emails on Day 14 of warmup:

• Gmail may accept all 50k inbox if engagement is high (Gmail rewards engagement fast)
• Outlook treats it as a spike; routes 30% to Junk (Microsoft is volume-sensitive)
• Yahoo sees an unfamiliar pattern; routes 60% to Junk (Yahoo is conservative)
• iCloud silently drops 40% (Apple is strictest, gives least feedback)

A uniform warmup curve optimized for Gmail under-warms Outlook/Yahoo/iCloud. A uniform curve optimized for the slowest (iCloud) wastes Gmail's appetite. Per-ISP warmup matches each receiver's curve.

Per-ISP recommended curves#

If your audience is 50% Gmail + 30% Outlook + 15% Yahoo + 5% iCloud (typical US mix), uniform warmup at Day 14 = 75% volume. Per-ISP at Day 14 = ~52% volume but ~85% inbox-placement across receivers, vs ~65% uniform. Net more delivered.

Implementation in AcelleMail#

Tag subscribers by ISP#

The per-ISP segment lives in tags. Apply at import-time or via batch update:

-- Run once via tinker / migration to tag existing subscribers
UPDATE subscribers SET tags = JSON_ARRAY_APPEND(COALESCE(tags, JSON_ARRAY()), '$', 'isp:gmail')
  WHERE email REGEXP '@(gmail|googlemail)\.com$';
UPDATE subscribers SET tags = JSON_ARRAY_APPEND(COALESCE(tags, JSON_ARRAY()), '$', 'isp:outlook')
  WHERE email REGEXP '@(outlook|hotmail|live|msn)\.com$';
UPDATE subscribers SET tags = JSON_ARRAY_APPEND(COALESCE(tags, JSON_ARRAY()), '$', 'isp:yahoo')
  WHERE email REGEXP '@(yahoo|ymail|aol)\.com$';
UPDATE subscribers SET tags = JSON_ARRAY_APPEND(COALESCE(tags, JSON_ARRAY()), '$', 'isp:icloud')
  WHERE email REGEXP '@(icloud|me|mac)\.com$';

For ongoing imports, add the tag-by-ISP step to your import pipeline OR use AcelleMail's import wizard's tag-mapping feature.

Create per-ISP segments#

In your list, Segments → New segment with rule:

Tag contains 'isp:gmail'

Repeat for outlook, yahoo, icloud.

Daily warmup campaign per ISP#

Day 7 example: send to gmail-segment at 40% volume.

1. New campaign → recipients = gmail segment only
2. Sending limit = the day's gmail % × your full-volume target
3. Launch

Repeat with smaller volumes per outlook + yahoo + icloud segments same day.

Open the sending-server detail#

In AcelleMail's sidebar, click Sending → Sending servers. The list shows every server connected to this account with its status chip, sending limit, and last activity:

Click into the row you want to configure. The detail page surfaces Connection settings (host / credentials), Configuration (server name, default from, sending limit, bounce + FBL handler), and the Test connection / Send test email buttons in the toolbar:

Where the throttle lives#

Same sending-server detail → Configuration section. The Sending limit dropdown caps how many emails AcelleMail will hand to this server per unit of time (per minute / hour / day):

AcelleMail enforces the limit globally — when the rolling-window counter hits the cap, the queue holds back until the window slides. No throttling code in your campaigns; configure once per server.

Adjust the sending-limit-per-hour per-day per the curves above. As each ISP's reputation grows (verify via Postmaster Tools / SNDS / AcelleMail's per-domain bounce mining), step up that ISP's volume independently.

Use a warmup strategy preset#

AcelleMail's admin Warmup Strategies screen ships with 4 preset curves you can attach per-server — Cautious, Balanced (default), Aggressive, Long-Haul:

For per-ISP warmup, the safest pattern: attach Long-Haul to servers targeting Microsoft/Yahoo/iCloud (conservative ISPs), Balanced to gmail-targeted servers. Mix by which ISP-tagged segment the server is reserved for.

Per-ISP signal sources#

For per-ISP AcelleMail-side mining, query your bounce_logs table:

SELECT
  SUBSTRING_INDEX(SUBSTRING_INDEX(email, '@', -1), '.', -2) AS domain,
  COUNT(*) AS bounces,
  SUM(CASE WHEN bounce_type = 'hard' THEN 1 ELSE 0 END) AS hard
FROM bounce_logs
WHERE created_at >= NOW() - INTERVAL 7 DAY
GROUP BY domain
ORDER BY bounces DESC
LIMIT 25

(Remember: prefix your table name with DB_TABLES_PREFIX if you have one — bounce_logs → acelle_bounce_logs in some installs.)

If yahoo.com bounces are 40% of all bounces but only 15% of your list, Yahoo-specific block. Pause yahoo segment; investigate at AcelleMail's Yahoo-postmaster-program contact.

Common UI signals + fixes#

#!/bin/bash
# Run at 03:00 daily. Auto-launches 4 per-ISP warmup campaigns based on
# current warmup day + per-ISP signal health.

DAY_OF_WARMUP=$1  # Pass current day as arg
ACELLE_TOKEN="..."
LIST_UID="..."
TEMPLATE_UID="..."

# Per-ISP daily volumes (from the curve table above)
declare -A GMAIL_VOL=([1]=5000 [3]=15000 [7]=40000 [14]=75000)
declare -A OUTLOOK_VOL=([1]=1000 [3]=3000 [7]=10000 [14]=30000)
declare -A YAHOO_VOL=([1]=1000 [3]=2000 [7]=5000 [14]=15000)
declare -A ICLOUD_VOL=([1]=500 [3]=1000 [7]=3000 [14]=8000)

for isp in gmail outlook yahoo icloud; do
  case $isp in
    gmail)   vol=${GMAIL_VOL[$DAY_OF_WARMUP]} ;;
    outlook) vol=${OUTLOOK_VOL[$DAY_OF_WARMUP]} ;;
    yahoo)   vol=${YAHOO_VOL[$DAY_OF_WARMUP]} ;;
    icloud)  vol=${ICLOUD_VOL[$DAY_OF_WARMUP]} ;;
  esac

  # Check yesterday's per-ISP signal — if bounce rate creeping up, skip today
  yesterday_bounce=$(curl -sH "Authorization: Bearer $ACELLE_TOKEN" \
    "https://acellemail.com/api/v1/campaigns/recent?tag=isp:$isp&days=1" \
    | jq '.aggregate.bounce_rate')

  if (( $(echo "$yesterday_bounce > 0.04" | bc -l) )); then
    echo "Skip $isp today — yesterday bounce $yesterday_bounce"
    continue
  fi

  # Launch today's per-ISP warmup campaign
  curl -X POST "https://acellemail.com/api/v1/campaigns" \
    -H "Authorization: Bearer $ACELLE_TOKEN" \
    -d "{
      \"name\": \"Warmup Day $DAY_OF_WARMUP — $isp\",
      \"list_uid\": \"$LIST_UID\",
      \"template_uid\": \"$TEMPLATE_UID\",
      \"segment_tags\": [\"isp:$isp\", \"engaged-last-7d\"],
      \"sending_limit\": $vol,
      \"schedule\": \"now\"
    }"
done

GATE: bounce <2% AND complaint <0.1% AND open >25% in last 24h for THIS isp
  YES → step up volume 20%
  NO  → hold today's volume; if 3 consecutive hold-days, cut volume 25%

for each tenant:
  for each (tenant, ISP) pair:
    fetch current warmup day
    fetch per-ISP signals
    launch / skip / hold today's campaign
    increment tenant.isp.warmup_day on success

Related articles#

• IP warmup schedule for new sending servers
• Microsoft SNDS walkthrough
• Gmail postmaster tools walkthrough
• Sender reputation monitoring
• Domain warmup