Smart Warming and how it applies to you

Smart Warming is an automated beehiiv process that gradually increases email sending volume on your custom domain to build its reputation with mailbox providers. It runs in the background and is enabled by default. Smart Warming applies in all of the following situations:

• Starting a new newsletter on a custom domain.
• Migrating an existing newsletter to a new domain.
• Migrating an existing newsletter from another platform to beehiiv.
• Sending using the shared beehiiv.com domain.

Smart Warming activates automatically when a custom domain is connected to your account. It triggers for publications sending to over 100 subscribers. If you set up your custom domain before reaching that threshold, Smart Warming will activate once your list reaches 200 subscribers.

The process builds a unified sending reputation across three elements tied to your custom domain: the domain name, the sender identity, and the IP address of the server sending your emails. All three must be established together. Even if your custom domain has been used for email sending before, it will still need to go through Smart Warming on beehiiv because the combination of your domain and beehiiv's IP address is new.

Smart Warming starts with a small subset of your subscribers receiving emails from your custom domain, while the rest receive emails from the beehiiv shared domain. Over time, the volume sent from your custom domain increases incrementally until all of your subscribers receive emails exclusively from your custom domain, marking the completion of the process.

For publications sending more than once a week, the process typically takes 6-8 weeks. Publications that send less frequently may take longer. Actual duration varies based on list size, sending frequency, and engagement signals from mailbox providers.

You can monitor the Smart Warming progress from the Domains page in your publication settings.

1. Click on Settings in the bottom left corner of your account.
2. Select Domains from the left panel.
3. Scroll down to the Email Domain section. If Smart Warming is active, a yellow tag will indicate Smart Warming In Progress.
4. Click the arrow next to Smart Warming to view the current status. A chart displays sending volume on the left axis and dates along the bottom. Hover over any point on the chart to view the exact sending volume for each domain.

When you send email from a domain and IP address combination that mailbox providers have not seen before, they have no basis for trusting it. Introducing high email volume from an unknown combination immediately can trigger spam filters, cause deferrals, or suppress inbox placement — even if your content is high quality and your list is engaged.

Smart Warming solves this by introducing your domain gradually, giving mailbox providers like Gmail, Yahoo, and Outlook time to observe consistent, positive sending behavior before your full list is in play. This protects your deliverability during transitions and sets your domain up for strong inbox placement long term.

Smart Warming is an adaptive process, not a fixed schedule. Several factors can slow progress or cause the system to pace more conservatively:

• Large list imports. If you import 200 or more subscribers and that import grows your list by 50% or more, Smart Warming will extend to account for the new volume. It resumes from where it was rather than restarting from the beginning. Imports below either threshold have no effect on the warming timeline.
• Limited sending volume. Smart Warming advances in stages, and each stage has a target send volume that must be met before the process moves forward. If you are not sending to your full subscriber list, or if your sending frequency is low, those stage thresholds may not be reached on schedule. Sending consistently and to your full list gives Smart Warming the best chance of completing on time.
• ESP signals. Mailbox providers like Gmail and Outlook sometimes signal beehiiv to slow down delivery, typically in response to high deferral rates or low open rates. When this happens, the Smart Warming algorithm adjusts automatically to protect your domain reputation. You cannot manually override this behavior.
• List hygiene. Importing unengaged or invalid contacts can trigger defensive signals from mailbox providers, slowing Smart Warming progress. Before migrating a large list to beehiiv, consider cleaning it to remove inactive subscribers and invalid addresses. For guidance, see Best email list cleaning services.

Your subscribers will not notice any difference during Smart Warming. They will continue to receive your newsletters as normal. The only thing that changes is which domain the emails are sent from during the ramp-up period.

All beehiiv features are available during Smart Warming, with one exception: A/B testing of email subject lines is unavailable until Smart Warming is complete. The A/B test toggle will be grayed out with a notice when you attempt to set up a split test.

Once Smart Warming finishes, typically 6-8 weeks for frequent senders, all of your emails will send exclusively from your custom domain.