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Gmail uses strict, adaptive spam filtering. New sending domains and IP addresses may be filtered or rejected if they have not built a positive reputation. This guide outlines a practical warm-up process. See Google’s Email sender guidelines for current requirements.

1. Complete the technical setup

Configure SPF, DKIM, and DMARC

  • SPF: Lists the servers allowed to send for your domain.
  • DKIM: Adds a signature that proves the message was authorized and not modified in transit.
  • DMARC: Tells Gmail how to handle messages that fail authentication and enables domain-abuse reporting.
During initial warm-up, consider a DMARC policy of p=none so you can monitor results before enforcing rejection.
See Add and verify a sending domain for configuration instructions.

Configure Google Postmaster Tools

Verify your sending domain in Google Postmaster Tools.
Google Postmaster Tools
Use it to monitor domain and IP reputation, authentication rates, delivery errors, and spam complaints.

2. Warm up gradually

Start with a small, high-quality, engaged audience and increase volume steadily.
  • Prioritize users active within the last 30 days who explicitly agreed to receive email.
  • Never warm up with purchased, stale, or unconfirmed lists.
  • Positive opens, clicks, and “not spam” actions help build reputation.
If complaints rise or open rates fall sharply, stop increasing volume and investigate content and list quality.
Avoid sudden spikes such as moving from 100 messages per day to 100,000.

3. Monitor and optimize

  • Keep spam complaints below 0.3%.
  • Keep hard bounces below 0.5% and clean invalid addresses.
  • Monitor opens and clicks as engagement signals.
  • Include a clear unsubscribe link in every message.
  • Send relevant content and avoid excessive capitalization, punctuation, or image-heavy layouts.
See Manage unsubscribes for unsubscribe setup.

Pre-send checklist

  • SPF, DKIM, and DMARC are configured correctly.
  • The domain is verified in Google Postmaster Tools.
  • The first audience contains recent, engaged Gmail users.
  • Volume increases gradually and consistently.
  • Complaint and bounce metrics are monitored.
  • Every message provides value and an easy way to unsubscribe.