Email warm-up is not just an essential step when you migrate from another email provider to Batch, with a new subdomain or set of IPs.
It is common to re-warm an IP or subdomain throughout its lifespan, in a wide variety of situations. Here are the cases where it's necessary:
New subdomains/IPs
Scheduling properly an email warm-up is a basic requirement whether you are:
Migrating to Batch
Senders typically perform an email warm-up, especially for a new pair of sending subdomain/IP addresses during a migration to a new email provider, to progressively build trust with inbox providers.
We have documented the whole warm-up methodology for subdomain & IP addresses here: subdomain & IP warm-up methodology.
Using subdomain for the first time
A warm-up is also required when you start using a new subdomain, to handle transactional messages for example (see our recommendations here).
Even with high email volume on your current shared or dedicated IP, the new subdomain needs to build its own reputation. Inbox providers value IP and sending domain reputation in different ways, and some may not fully leverage the IP's existing reputation.
If your IP address already has a strong reputation, and the subdomain you are planning to warm-up will not send large volumes of emails, you can try starting with larger batches of emails, instead of starting with a batch of 200 emails (see our recommended warm-up schedule here).
Introducing a different sending IP
A domain warm-up is always required when:
IP switch: Switching from one sending IP to another, which should remain a rare situation.
Additional IP address: When adding a new dedicated IP address to your sending pool.
Warmed-up subdomains/IPs
Planned volume increases
Inbox providers often value sending regularity and stable volume for sending domains/IPs, to detect suspect patterns that require to protect their users. Take a look at major inbox providers guidelines to know more on that part (see "Increase sending volume slowly", in Google's sender guidelines)
This is why every substantial change in the volume of sent emails / day should be implemented progressively, following the see our recommended warm-up schedule here.
Senders restarting after a break, or with a bad sending permanence
For senders restarting after a break or with a bad sending permanence, consider a brief subdomain warm-up. While not as extensive as a new subdomain warm-up, avoid sending large email volumes initially.
Start low, engage high:
Resume sending with lower volumes (1-2 steps below previous, see scale here)
Focus on highly engaged users initially.
Significant sending changes
Inbox providers value consistency.
Sudden changes in sending patterns or new content can raise red flags.
Consider executing a short warm-up when you:
Implement a new tracking domain for email analytics.
Introducing a completely redesigned email template or change drastically the structure of your emails.
And more
By proactively warming up your sending reputation, you can minimize email delivery disruptions and ensure your messages reach your intended audience.