If you're changing email platforms as part of a replatform, start the warm-up four to six weeks before you flip DNS on the new store, and start it with the people who opened something in the last 30 days. That's the short version. Email deliverability domain warmup is just the process of teaching Gmail, Yahoo and Outlook that a new sending domain belongs to someone who sends mail people want, and the only evidence they accept is opens, clicks, replies and a very low complaint rate. You cannot buy that. You can only accumulate it, slowly, before launch day, while the old store is still quietly doing its job.
Here's the part that usually gets skipped in the migration plan: your abandoned-cart flow, your welcome series and your first launch campaign all fire in the same 72-hour window. On a cold domain, that is exactly the pattern spam filters are built to catch.
First, check whether you actually need a warm-up
Plenty of migrations don't. Reputation attaches mostly to the sending domain and the IP, so if you're keeping news.yourbrand.com as your From domain and simply repointing the authentication records from one ESP to another, a lot of your history travels with you. Gmail's view of your organisational domain doesn't reset because you switched from Mailchimp to Klaviyo.
You need a real warm-up when one of these is true:
- You're moving to a brand-new domain name, or a new subdomain with no sending history
- Your old sending domain has a bad reputation and you're deliberately walking away from it
- You were relying on your old platform's shared mail service and never authenticated your own domain at all, which is common on Magento and WooCommerce builds where transactional mail went out through the host
- You're going from a few thousand sends a month to a few hundred thousand because the migration comes with a list consolidation
If none of those apply, spend the time on your flows instead. A warm-up you don't need costs you four weeks of revenue for no gain.
Get the DNS right before you send a single email
Warm-up on an unauthenticated domain is wasted effort. Since Google and Yahoo tightened their bulk-sender rules in early 2024, the baseline is non-negotiable: SPF and DKIM that both align with the domain in your From address, a DMARC record on the organisational domain, valid reverse DNS on the sending IP, and one-click unsubscribe headers on marketing mail.
Practical notes from doing this on live stores:
- Send marketing from a subdomain, not the root. Something like news.yourbrand.com or hello.yourbrand.com. If a campaign ever tanks your reputation, the damage is contained and your invoices and support replies from the root domain keep landing.
- Publish DMARC as p=none first with a reporting address, read the aggregate reports for a fortnight, then move to quarantine and later reject. Going straight to p=reject during a migration is how you discover, live, that your transactional shipping notifications were being sent by a courier plugin nobody documented.
- Watch the TTL. Drop TTLs on relevant records to 300 seconds a few days before cutover so mistakes are cheap to undo.
- One record set per sender. SPF has a ten-DNS-lookup limit and Indian stacks pile up senders fast: ESP, Shopify, a WhatsApp tool, a helpdesk, a review app, an invoicing tool for GST-compliant invoices. We've seen SPF quietly break because someone added a seventh include.
A warm-up ramp with real numbers
Take a 60,000-address list. Pull everyone who opened or clicked in the last 30 days — say that's 9,000 — and everyone in the 31-to-90-day window, another 9,000. The remaining 42,000 do not exist for the next month.
A ramp that works on a Shopify store with a decent Gmail-heavy list looks roughly like this:
- Send 1 — 1,000 recipients, all 30-day engaged
- Send 2, two days later — 2,000
- Send 3 — 4,000
- Send 4 — 8,000
- Send 5 — 9,000, the full 30-day segment
- Send 6 onward — start folding in the 31-to-90-day group, 4,000 at a time
That's about 18,000 addresses reached over roughly two and a half weeks, with volume roughly doubling each step. Now the checks. Gmail publishes a spam-complaint ceiling of 0.3% and tells senders to aim below 0.1%. On that 8,000-recipient send, 0.1% is eight complaints and 0.3% is twenty-four. If you cross twenty-four, you don't push to the next tier — you go back a step and fix the content or the segment. Same logic on bounces: if hard bounces on send one come in above 2%, that's twenty addresses out of a thousand and your list hygiene is the problem, not your domain.
Two more things that move the needle more than volume pacing. Ask for a reply in the first two or three emails, genuinely — a one-question survey, a "what are you shopping for" reply-to. Replies are a strong positive signal and almost nobody bothers. And keep the subject lines boring. Save the emoji-heavy 40%-off subject line for week five.
Where domain warm-up sits in the replatform timeline
The sequencing matters more than the technique. On a typical Shopify migration we work backwards from the cutover date:
T-6 weeks. Decide the sending subdomain. Publish SPF, DKIM and DMARC for the new ESP. Import the list into the new platform but keep it unsubscribed from everything except a single manual campaign segment. Import your suppression list first, before anything else — old unsubscribes, old hard bounces, old complainers. This is the step most often missed, and it's the one that ruins a warm-up in a single send.
T-5 to T-2 weeks. Run the ramp above using content that works on the old store. Newsletters, restock notes, a story email. Links point at the live site, so the emails have to be worth sending on their own merit. This is also when you find out that your 90-day engaged segment is a third of the size finance assumed.
T-1 week. Full engaged-segment volume reached. Flows built and tested in the new platform, but still switched off. Send yourself through every flow using a real test order, including a COD order, because COD confirmation mail is the one your ops team will get called about.
Cutover week. Turn flows on in stages, not all at once. Order confirmation and shipping first, then welcome, then browse and cart abandonment on day two or three. Watch the flow-level delivery numbers for 48 hours before you send the launch campaign.
T+2 weeks onward. Begin reintroducing the 90-to-180-day segment in small batches. Anyone with no engagement in a year stays suppressed. If that feels like throwing away a list you paid for, run the arithmetic: 42,000 dead addresses that produce nothing and drag your inbox placement down are a liability with a hosting bill.
Transactional email needs its own decision
Shopify sends order confirmations, shipping updates and password resets from its own infrastructure by default. If you want those to come from your own address, Shopify asks you to authenticate the domain with DNS records. Do it, but keep transactional on a different subdomain from marketing — orders.yourbrand.com versus news.yourbrand.com. Transactional mail has near-perfect engagement and almost no complaints. Marketing mail does not. Mixing them means a bad campaign can push order confirmations to spam, and on a COD-heavy Indian store that's a direct hit on your confirmation rate and your RTO numbers.
Transactional streams also warm themselves. Real orders, real opens, low volume at first. You mostly don't need to do anything except get the DNS right and not route them through the same subdomain as your Diwali sale blast.
Dedicated IP: probably not
Most Shopify brands we work with should stay on their ESP's shared pool. A dedicated IP only helps once you're sending enough consistent volume to keep it warm — think a few hundred thousand emails a month, sent regularly, not two big campaigns in a festive quarter. Below that threshold a dedicated IP gives you an unwarmed IP and an unwarmed domain, and long gaps between sends where the IP goes cold again. Shared pools are already warm. Take the free ride.
What to watch, and where
Set these up before send one, not after something breaks:
- Google Postmaster Tools, verified for the sending domain. It's the only honest window into how Gmail rates you, and for most Indian D2C lists Gmail is the majority of the file. Domain reputation should climb from "low" or blank toward "high" over the ramp.
- Microsoft SNDS if a meaningful share of your list is on Outlook or Hotmail. Outlook is a separate personality with a longer memory.
- Your ESP's per-domain delivery breakdown. An overall open rate of 34% can hide a Gmail open rate of 42% and a Yahoo open rate of 6%, which is a placement problem wearing a costume.
- Seed inbox tests across Gmail, Outlook, Yahoo and one Indian ISP. Useful directionally. Don't treat a placement report as truth.
Don't schedule the warm-up into your peak
Mailbox providers get stricter when global volume spikes, and everyone's volume spikes at the same time. A cold domain trying to ramp during the last week of Navratri, or through BFCM, is fighting the entire internet for inbox space. If your replatform is landing in September or October, either finish the warm-up by mid-August or accept that the first festive campaign goes out on the old platform while the new domain keeps ramping in the background. We've made that call more than once. It's less painful than losing the Diwali sale to the promotions tab.
The failure modes we see most
Someone imports the full list and sends a launch announcement to 60,000 people on day one from a domain with zero history. Recovery from that takes six to eight weeks of disciplined sending, and some of that reputation never fully comes back — you're better off retiring the subdomain and starting again on a fresh one.
Second: suppression lists left behind on the old platform. Every unsubscribe you forget is a complaint waiting to happen, and complaints from people who opted out years ago are the most expensive kind.
Third, and this one is specific to India: lists built from COD checkouts full of typo'd and throwaway addresses. Run a validation pass before the first send and drop anything that fails. Paying to clean 60,000 records is cheaper than a month of bad placement.
Fourth: flows switched on the moment the theme goes live because nobody owned the email side of the cutover. Put a name against it in the launch checklist. If your build is being handled by an outside team, make sure deliverability is in scope — it sits between the developer and the marketer, which is exactly why it falls through. Our Shopify developers and email side work off the same launch plan for this reason.
If you're three months out from a replatform, the useful next step is small: pull your engaged-subscriber counts at 30, 90 and 180 days, and check today whether SPF, DKIM and DMARC are published and aligned for every service that sends mail as your brand. That one audit tells you whether your warm-up is a two-week job or a six-week one. Happy to look at it with you as part of a free store audit.