Mailbox Warming: What Happens When You Change a Domain or Sender?

Overview

When updating your email setup in Unify, mailbox warming requirements vary depending on what type of change you’re making. Whether you’re introducing a brand-new domain or updating the name on an existing mailbox, understanding these timelines helps you plan outbound campaigns without impacting deliverability.

This guide breaks down warming requirements by change type and shares best practices to keep your sending reputation healthy.

Warming Requirements by Change Type

New Domain Changes

Estimated Warming Time: ~3 weeks

If you’re switching to a completely new sending domain (for example, moving from company1.com to company2.com), a full warming cycle is required.

Key things to know:

• New domains require the complete ~3-week warming period

• This applies even if the domain was previously used on another email platform

• Domains do not inherit warming or reputation history

• Outbound volume will be intentionally limited during this period to protect deliverability

Best for: Long-term outbound strategy, net-new domains, or when starting fresh for reputation reasons.

Same Domain, Different Person

Estimated Warming Time: ~1 week

If you’re keeping the same domain but changing the sender name on the mailbox (for example, replacing “Cassandra” with “Lindsay”):

• Only a short warming period (about 1 week) is needed

• The domain’s existing reputation remains intact

• Ideal for team changes, backfills, or role transitions

• Significantly faster than spinning up a new domain

Best for: SDR turnover, new hires, or reassigning ownership of an existing mailbox.

Important Notes

• Mailbox warming is managed by Unify to protect domain and sender reputation.

• Fresh domains are often recommended over transferring previously used ones for optimal deliverability.

• Warming timelines are estimates and may vary based on sending behavior and domain health.