💡 Goals:
Define a warm-up goal for each subdomain.
Know how long your warm-up process should last for each subdomain.
📌 Deliverables:
Defining a warm-up goal
The warm-up goal is the average volume of emails you need to be able to send every day from your subdomain.
Defining a warm-up goal per sending subdomain is the first step to schedule properly the whole process. Your warm-up goal is the maximum amount of emails you send in average in a single day.
📌 Todo: Based on the work done in the step 1, analyze the figures in the tables to determine, for each each category, the maximum volume of emails you need to be able to send in a single day.
| 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 |
Reminder: If you have read our guide on email sending structure, you should know that every email category should match a sending subdomain for resiliency purposes.
Estimating the warm-up duration
The objective of an email warm-up, 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:
Start small (e.g. 200 emails the first day)
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)
Once you reach 100K emails/day, slow down and increasing the volumes using a x1,5 factor (e.g. Day 11: 100K emails → Day 12: 150K emails).
Once you reach 400 emails/day, slow down again, and only increase the volumes using a 1,25 factor (e.g. Day
📌 Warm-up timeline example
Week 1 | Daily sent emails |
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 |
📌 Basic warm-up schedule example
You can deduce the warm-up duration for your subdomain based on that warm-up goal. A warm-up process generally takes from a few days to several weeks.
→ E.g. I send 6.4K emails/day from my transactional subdomain.
Based on the scale described above, the warm-up process should last 6 days.
| 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: