IP Warm-Up Best Practices

When migrating ESPs, you will start sending from a brand new IP address. Inbox providers like Gmail, Outlook, and Yahoo see that IP as an unknown sender. If you immediately start mailing to your full email list right away, you risk landing in spam or getting throttled. The best practice here is IP warming — gradually building your sending reputation while following deliverability hygiene rules. Here’s a detailed checklist for success:

Key Rules During Warm-Up

1. Ramp up send volume gradually and don't increase volume if:

1. Bounce rate > 2%
   
2. Spam complaint rate > 0.1%
   
3. Open rates drop significantly
   

Instead, repeat the previous day’s volume or drop back to previous days volume.

2. Monitor these metrics daily

1. Open & click rates (positive engagement)
2. Bounce & spam complaint rates (negative signals)
3. Reputation via tools like Google Postmaster Tools, Microsoft SNDS

3. Keep sending cadence consistent: Sudden changes in timing, volume, or from-address can hurt reputation building.

4. Avoid sending to inactive subscribers until the end: These can trigger spam traps and lower engagement during warm-up.

Start Slow & Ramp Up Gradually

Why: ISPs monitor sending patterns from new IPs. A sudden spike looks like spam behavior.

How: Send to small volumes at first, then increase volume no more than 50% daily if engagement stays high.

Our Deliverability team suggests an initial daily increase of no more than 20% to be safest during your first few days.

Example warm-up schedule:

1. Day 1: 500 emails to your most engaged subscribers
2. Day 2: 1,000
3. Day 3: 2,000
4. Continue until full volume is reached

Adjust numbers for your total list size & engagement rates.

Target the Most Engaged Recipients First

Why: Positive engagement (opens, clicks, replies) signals trust to ISPs.

How: Segment your list by recent activity — start with people who opened or clicked in the last 30–60 days.

❌ Avoid sending to inactive, unverified, or old addresses during warm-up.

Authenticate Your Sending Domain

1. Set up these authentication methods correctly before sending:

1. SPF (Sender Policy Framework)
2. DKIM (DomainKeys Identified Mail)
3. DMARC (Domain-based Message Authentication, Reporting & Conformance)

2. Use the same sending domain as your brand (avoid generic ESP domains).

3. Consider using custom tracking domains for brand alignment.

Keep Content Clean & Consistent

1. Use the same sender name and email address throughout warm-up.

2. Avoid spam-triggering elements:

1. Excessive ALL CAPS or !!! in subject lines
2. Overuse of promotional buzzwords (“FREE!!!”)
3. Large, single-image emails with little text

3. Keep text-to-image ratio healthy (roughly 60/40 text-to-image).

Monitor Engagement & Deliverability Daily

1. Keep a close eye on these metrics:

1. Open rates
2. Click-through rates
3. Bounce rates
4. Spam complaint rates

2. If positive metrics drop or bounces spike:

1. Pause volume growth — repeat previous days volume for next send
2. Re-focus on the most engaged segment again
3. Investigate potential issues — content or new lists sources (not opt-in, unverified?)
   
   

Maintain Ongoing List Hygiene

1. Remove hard bounces from your active email list immediately, even after warm-up phase.

2. Suppress unengaged users (e.g., no opens in 90+ days) from regular mailing lists.

3. Validate addresses before importing into and sending from new ESP.

Respect Sending Frequency & Consistency

1. Don’t send erratically (e.g., 1,000 today, 50,000 tomorrow).

2. Establish a rhythm ISPs can “learn” and trust.

Example Slow Warm-Up Plan (List size 100k)

250 Start → 100k in Final Week

55-day schedule, volume growth ~18% daily average

Day	Sends	% ↑ vs prev day	Notes
1	250	—	Target most engaged subscribers first.
2	295	18.0%
3	348	18.0%
4	411	18.1%
5	485	18.0%
6	572	18.0%
7	675	18.0%	End Week 1 — review bounce/spam rates.
8	797	18.1%
9	941	18.1%
10	1,110	18.0%
11	1,311	18.1%
12	1,540	17.5%
13	1,815	17.8%
14	2,139	17.9%	End Week 2 — start adding moderately active contacts.
15	2,522	17.9%
16	2,972	17.8%
17	3,503	17.9%
18	4,123	17.7%
19	4,854	17.7%
20	5,715	17.8%
21	6,727	17.7%	End Week 3 — include less-engaged but verified addresses.
22	7,915	17.7%
23	9,306	17.6%
24	10,930	17.5%
25	12,821	17.3%
26	15,018	17.1%
27	17,570	17.0%
28	20,532	16.8%	End Week 4 — by now you’re sending to ~20% of your list.
29	23,992	16.9%
30	28,031	16.8%
31	32,725	16.8%
32	38,173	16.6%
33	44,495	16.5%
34	51,834	16.5%
35	60,362	16.5%	End Week 5 — still not at full volume, reputation is stabilizing.
36	70,238	16.3%
37	81,676	16.3%
38	94,856	16.1%
39	100,000	5.4%	First full-volume day — monitor closely for any deliverability dips.
40–55	100,000	0%	Maintain full sending volume and cadence to reinforce IP reputation — if deliverability and engagement is stable.

Why this works best for a new IP

1. Slower ramp-up gives ISPs more consistent data, lowering the risk of throttling or spam-folder placement.

2. Holds engagement high in early weeks by targeting only your most active contacts first.

3. Grows into the full list gradually, so by the time you’re sending to everyone, you already have a positive sender reputation.

Got Questions?

Reach out to Support by phone: 866.915.9465 or email: support@delivra.com

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