It doesn't matter if you wrote the Shakespeare of emails; if it lands in the Spam folder, you failed. Deliverability is a reputation game played against AI algorithms.
1. Warm Up Your IP
New IP addresses are "cold" and suspicious. If you buy a new dedicated IP and send 100,000 emails on Day 1, you will be blocked. The Warm-up:
- Week 1: 50 emails/day
- Week 2: 100 emails/day
- Week 3: 500 emails/day
- Week 4: 1,000 emails/day This teaches ISPs (Gmail, Outlook) that you are a legitimate sender with consistent traffic.
2. List Hygiene (Hard vs Soft Bounces)
- Hard Bounce: The email address doesn't exist. Action: Delete immediately. Repeatedly sending to non-existent users is a huge red flag.
- Soft Bounce: Mailbox full or server down. Action: Retry 3 times, then delete.
- Sunset Policy: If a user hasn't opened an email in 6 months, stop sending to them. Low engagement rates drag down your reputation for everyone.
3. Make Unsubscribing Easy
If users can't find the "Unsubscribe" button, they will hit "Mark as Spam." A spam complaint is 100x worse for your reputation than an unsubscribe. Put the link clearly at the top or bottom. Use a "One-Click Unsubscribe" header in your emails.
4. Content Triggers
Avoid spammy words like "FREE", "CASH", "URGENT", "WINNER" in the subject line. Keep your HTML clean and balance image-to-text ratio (60% text, 40% images). All-image emails are often flagged because spammers use them to hide text.