Cold Email Mailbox Calculator
Plan your cold email infrastructure. Enter your daily sending volume and get a breakdown of domains, mailboxes, estimated costs, and warmup timeline.
Industry standard is 30–50 per mailbox
Mailboxes
16
13 base + 3 warmup
Domains
6
3 mailboxes/domain
Monthly Cost
$102
$96 hosting + $6.00 domains
Warmup Time
3wk
Before full capacity
Weekly: 2,500 emails
Monthly: 10,000 emails
What is Cold Email Mailbox?
When running cold email campaigns, sending too many emails from a single mailbox damages your sender reputation and triggers spam filters. Best practice is to distribute your volume across multiple mailboxes (30-50 emails per mailbox per day) on multiple domains (2-3 mailboxes per domain). This calculator helps you plan the right infrastructure.
How to Use This Tool
Enter Your Daily Volume
How many cold emails do you want to send per day? Be realistic — start with your current target and scale up over time.
Adjust Settings
Fine-tune emails per mailbox (30-50 is the safe range), working days, and whether to include a warmup buffer for redundancy.
Plan Your Infrastructure
Use the results to purchase the right number of domains and set up mailboxes. Connect them to TrulyInbox for automated warmup before launching campaigns.
Frequently Asked Questions
Sending more than 50 cold emails per day from a single mailbox risks triggering spam filters and damaging your sender reputation. Distributing volume across multiple mailboxes keeps each one within safe sending limits.
Using 2-3 mailboxes per domain is best practice. If one domain's reputation is damaged, it doesn't affect your other domains. It also looks more natural to email providers.
30-50 emails per mailbox per day is the generally accepted safe range for cold email. New mailboxes should start lower (10-20/day) and scale up gradually during warmup.
A warmup buffer adds 20% extra mailboxes to your plan. These spare mailboxes ensure you can maintain your sending volume even if some mailboxes need to be rested or replaced.
The main costs are domain registration (~$10-15/year per domain) and email hosting (~$6/month per mailbox for Google Workspace or Microsoft 365). The calculator estimates total monthly costs based on these prices.
Email warmup typically takes 2-4 weeks. During this period, TrulyInbox sends and receives warm emails to gradually build your sender reputation before you start cold outreach.