Step 4 - Estimate Your Warmup Target

Avoiding common pitfalls with audience selection and timing when elaborating your subdomain warm-up schedule.

1

💡 Goals

• Define a warmup goal for each subdomain

• Know how long your warmup process should last for each subdomain

2

📌 Deliverables

• Warmup goal, one per sending subdomain

• Warmup schedule, one per sending subdomain

Defining a Warmup Target

The warmup target is the average volume of emails you need to be able to send every day from your subdomain. Defining a warmup target per sending subdomain is the first step to properly schedule the whole process. Your warmup goal is the maximum amount of emails you send on average in a single day.

In the table below, define the maximum volume of emails you need to be able to send in a single day.

📌 Warmup Targets table

Message type	Warm-up goal	Estimated duration
Transactional automations	x emails/day	x days
Marketing automations	x emails/day	x days
Email campaigns	x emails/day	x emails/day

Make sure this doesn't include inactive subscribers (see Step 3 - List Hygiene Review).

Estimating the Warmup Timeline

→ Understanding the Volume Increase Methodology

The objective of an email warmup is to gradually increase the number of emails sent from a new email subdomain/IP to establish its reputation with inbox providers.

The general rule is to:

1. Start small (e.g., 200 emails the first day)

2. Increase progressively the volume of sent emails, never sending more than twice than the day before (e.g., Day 1: 200, day 2: 400, day 3: 600, etc.).

3. Once you reach 100K emails/day, slow down and increase the volumes using a x1.5 factor (e.g., Day 11: 100K emails → Day 12: 150K emails)

4. Once you reach 400K emails/day, slow down again, and only increase the volumes using a 1.25 factor

📌 Warm-up timeline example

Time	Volume of sent emails
Week 1
Day 1	200
Day 2	500
Day 3	1K
Day 4	2K
Day 5	5K
Day 6	10K
Day 7	20K
Week 2
Day 8	40K
Day 9	50K
Day 10	75K
Day 11	100K
Day 12	150K
Day 13	200K
Day 14	250K
Week 3
Day 15	325K
Day 16	400K
Day 17	500K
Day 18	600K
Day 19	750K
Day 20	1M
Day 21	1.25M

If you are warming up new IPs, we recommend you increase the volumes more progressively:

• Day 1: 200 emails sent

• Day 2 : 200 emails sent

• Day 3 : 500 emails sent

• Day 4 : 500 emails sent

• Etc

→ Define Your Warmup Timeline

You can deduce the warm-up duration for your subdomain based on your warm-up target, which is the maximum volume of emails you need to be able to send in a single day.

Example: If you send 6.4K emails/day, based on the scale described above, the warm-up process should last 6 days.

Stage #	Daily sent emails
Stage 1	200
Stage 2	400
Stage 3	800
Stage 4	1600
Stage 5	3200
🎉 Final stage	6400

Scheduling a warm-up

→ Avoid tight schedules

During the warm-up phase, delivery stability can be unpredictable. Inbox providers may react variably to volume increases from unfamiliar senders—they might accept all your emails, delay some, or even block your subdomain or sending IP without notice. Therefore, the warm-up process often requires adjustments based on the response from each inbox provider.

Some emails, such as transactional messages (e.g., password resets), are critical for your business. We recommend adding an additional 2-week buffer period. This allows you to address any issues with providers proactively and reset if necessary.

→ Find the best moment to start your warm-up

Some moments of the weeks and of the year are far from ideal.

Avoid starting a warm-up:

• When no one is available to monitor the delivery of your emails and to ask for a mitigation.

• When inbox providers likely cannot answer tickets (e.g. during the weekend).

• When your recipients don't read their emails (e.g. during the weekend, depending on your business) or when they are not interested by your emails.

• When your recipients are already receiving more emails than usual (e.g. Black Friday, Christmas, etc), as this would decrease the amount of opens and clicks for your emails.

→ Sending permanence is key

Be sure you maintain a good sending permanence during the whole process:

• Don't stop sending emails during the weekend. You should send emails every day.

• If you are warming up a subdomain that will send newsletters, focus on emails that are not time sensitive (e.g. with offers that don't expire, etc). This is important because you will be sending the same newsletter to different batch of users across several days or weeks.

Next step

Let's prepare your campaigns/automations migration schedule now:

Step 5 - Warmup Schedule