How to avoid email going to spam

Quick answer: Deliverability rests on four pillars: a correct PTR record, passing SPF/DKIM/DMARC, a clean IP and domain reputation, and sane sending behaviour (opt-in lists, steady volume, working unsubscribe). Miss any pillar and filters will punish you.

Overview

Spam filtering is scoring, not a single rule: authentication, reputation, content and recipient engagement all add up. You control every input — this checklist orders them by impact so you fix the cheapest, most powerful items first.

Before you start

• A test mailbox at each major provider you care about (Gmail, Outlook).
• Access to your DNS zone and your mail server logs.

Step-by-step guide

1. Infrastructure: PTR matching your mail hostname, hostname matching the SMTP HELO, TLS enabled.
2. Authentication: SPF, DKIM and DMARC all showing pass in the Authentication-Results header of a test message.
3. Reputation: confirm the IP is on no major blacklist — how to check. Warm a fresh IP up gradually: small volumes to engaged recipients first, growing over weeks.
4. List hygiene: only opt-in recipients, remove hard bounces immediately, honour unsubscribes instantly — also required by the abuse policy.
5. Content: balanced text-to-image ratio, no link shorteners, a plain-text part alongside HTML, consistent From name and address.
6. Monitoring: watch bounce codes in the mail log and re-test after every infrastructure change.

Common issues

• Everything passes but Gmail still filters: a new IP/domain has no history — engagement warm-up takes time; consistency wins.
• Sudden drop after months of fine delivery: check for a blacklist entry or a compromised account/script sending spam from your server.
• Marketing blasts from the same IP as business mail: separate the streams — transactional mail should not share fate with newsletters.

When to contact support

If your IP appears on a blacklist you believe is due to a previous holder, or you plan legitimate higher-volume sending and want to stay within policy, open a ticket before you start.

Frequently asked questions

What is the single most common cause of spam-foldering?

A missing or generic reverse DNS record combined with incomplete SPF, DKIM or DMARC — authentication gaps outweigh content issues in modern filtering by a wide margin.

How do I warm up a new sending IP?

Start with small daily volumes to your most engaged recipients and grow gradually over several weeks; sudden volume from a fresh IP is a classic spam signal to providers.

Does message content still matter for filtering?

Yes, but less than authentication and reputation. Keep a text part alongside HTML, avoid link shorteners and misleading subjects, and stay consistent in sender name and address.

Related articles

• How to check IP reputation
• How to set reverse DNS / PTR record
• Common email delivery issues
• Email sending limits and abuse policy

Need a hand? Contact Cloud2Y support →