Email Deliverability Tips:
17 Ways to Keep Emails Out of Spam

Email deliverability tells you whether your messages actually make it to the recipient’s inbox. Some mail is rejected before delivery, and some gets accepted but filtered to spam. Mailbox providers make that call based on domain and IP reputation, authentication, sending patterns, list quality and recipient engagement.

Start with SPF, DKIM and DMARC. Warm up new domains and mailboxes gradually, then keep the sending schedule steady. Verify your list before every campaign. Remove inactive contacts and make it easy to unsubscribe. Check inbox placement regularly so you can spot problems early.

Most healthy sending programs have inbox placement above 90 percent. Bounce rates are usually under 2 percent, with spam complaint rates below 0.1 percent. Don’t rely on one blended number, though. Placement can differ from one mailbox provider to another.

Delivery just means the receiving server accepted the message. Deliverability tells you where an accepted message lands. That can be the inbox, Promotions or spam. A campaign can report 99 percent delivery even when most emails end up in spam. That’s why placement needs to be checked separately.

Spam placement usually comes down to several different issues. Authentication can fail or be misaligned. Domain or IP reputation may be damaged. High bounce or complaint rates, sudden volume increases, blocklist entries and content that trips filters are other common causes. Check them one by one.

They don’t guarantee inbox placement. Without those records, many providers won’t trust the message. Bulk senders also need them for Gmail, Yahoo and Outlook.com. Proper alignment shows that you control the domain and helps protect your brand from spoofing. That protects your reputation too.

A new domain usually needs several weeks of gradual, consistent sending before it can handle meaningful volume. Warmy’s guideline is around two to four weeks, but the timeline isn’t fixed. Target volume, provider mix and engagement all affect it. Automated warm-up adjusts the pace from day to day instead of following the same schedule every time.

Yes. A heavy image-to-text ratio, broken HTML, link shorteners, poor-reputation link domains and misleading subject lines can raise filter scores. But filters are only part of it. Content people actually want to read creates the engagement signals that help keep your reputation strong.

Senders of 5,000+ messages a day to Gmail need SPF and DKIM, a DMARC policy, From-domain alignment and one-click unsubscribe. Unsubscribe requests must be honored within two days, and the spam rate must stay below 0.3%. Yahoo’s rules are similar. Since May 2025, Outlook.com has applied SPF, DKIM and DMARC requirements to high-volume senders.

Run a deliverability test and see where your message lands across the providers that matter to you. Warmy’s free Email Deliverability Test shows whether test emails reach the inbox, Promotions or spam. It also checks authentication and blocklists.

Cold email is sent from regular mailboxes to people who don’t already have a relationship with you. Warm-up, low daily volume per mailbox and replies matter more here. Marketing email goes through an ESP to people who opted in. For marketing email, pay more attention to authentication, list hygiene, one-click unsubscribe and engagement over time.

Test every new campaign or template. Run another test after changes to your sending setup, such as a new domain, ESP or DNS record. If you send regularly, test at least once a week. Placement can change without warning. Regular checks help catch problems before they affect your whole list.

No. Bulk senders have to provide one-click unsubscribe. An easy opt-out helps reduce spam complaints, and a complaint does far more damage than an unsubscribe. For cold email, a simple text opt-out line works.