What Is Domain Warm-up?

When you start sending emails from a new domain, email providers (Gmail, Outlook, Yahoo) don't yet trust your domain. If you send thousands of emails immediately, they may be flagged as spam. Domain warm-up is a gradual process: you start with a smaller daily sending volume and increase it over several days, building a positive reputation with inbox providers.

MailerBit handles warm-up automatically. During the first days of your subscription, your daily sending limit increases progressively. After the warm-up period, you have full access to your plan's monthly email quota with no daily cap.

A properly warmed domain achieves significantly higher open rates and lower spam rates. Skipping warm-up is one of the most common reasons new senders end up in the spam folder — MailerBit eliminates this risk entirely by automating the process for you.

Why We Require Domain Verification

Unlike platforms that let you send from a shared domain, MailerBit requires you to verify your own domain with DKIM and Return-Path DNS records. This means:

• Your emails come from your domain, not a shared address — boosting trust and brand recognition.
• Higher inbox placement — authenticated domains pass DKIM/SPF checks, reducing spam filtering.
• Isolated reputation — your deliverability is never affected by other users' sending behavior.

DKIM & Return-Path Explained

DKIM (DomainKeys Identified Mail) is a DNS record that lets receiving mail servers verify that your email was genuinely sent from your domain and was not tampered with in transit. It works by attaching a cryptographic signature to every outgoing email that can be validated against a public key in your DNS.

Return-Path is a DNS record (also known as a custom bounce address) that routes bounced emails back through your domain. Setting a custom Return-Path further strengthens authentication and improves deliverability scores with major inbox providers.