Email Deliverability: Why Your Email Blasts Land in Spam and How to Fix It

If your email blasts are landing in spam, the cause is usually one of three things: your domain is not properly authenticated, you are sending to people who did not ask for your mail or no longer read it, or the message itself looks like bulk junk. Good email deliverability comes from fixing all three, starting with authentication, because no amount of good writing helps a message that never reaches the inbox.

This guide explains how inbox providers decide where your mail goes, what Google and Yahoo now require from bulk senders, and a practical checklist for small businesses that send newsletters, promotions or announcements to a list.

What Email Deliverability Actually Means

Delivery and deliverability are different things. A message is “delivered” when the receiving server accepts it. Deliverability is whether it lands in the inbox, the promotions tab or the spam folder. Your email tool may report nearly every message as delivered while many of them sit in spam folders where nobody sees them.

Inbox providers such as Gmail, Outlook and Yahoo make that placement decision for every message, based mostly on three questions:

• Is this sender who they claim to be? That is authentication.
• Do recipients want mail from this sender? That is reputation, built from opens, replies, deletions, spam complaints and bounces over time.
• Does this message look like spam? That is content and formatting.

Step 1: Authenticate Your Sending Domain

Authentication lets receiving servers confirm that mail claiming to be from your domain really came from you. There are three standard records, all added in your domain’s DNS settings:

• SPF lists the servers and services allowed to send mail for your domain. If you send through an email marketing service, it must be included in your SPF record. A domain should have only one SPF record, so add services to the existing record instead of creating a second one.
• DKIM adds a digital signature to each message. Your email service gives you the records to add; once they are in place, receiving servers can verify that the message was not altered.
• DMARC tells receiving servers what to do when a message fails SPF and DKIM checks, and can send you reports. Many businesses start with a monitoring-only policy, review the reports, then tighten it.

One detail trips up many small businesses: send from an address on your own domain, not a free webmail address. Free mailbox providers publish strict DMARC policies, so bulk mail that claims to come from one of their addresses but is sent through a marketing tool is likely to be rejected or filtered.

What Google and Yahoo Require From Bulk Senders

In 2024 Google and Yahoo began enforcing stricter rules for anyone sending large volumes to their users. Google’s sender guidelines say that all senders need SPF or DKIM, and that senders who send close to 5,000 or more messages a day to Gmail accounts must also:

• Set up SPF, DKIM and DMARC for their sending domain.
• Make sure the visible From domain aligns with the domain that passes SPF or DKIM.
• Include one-click unsubscribe in marketing messages and process unsubscribes within two days.
• Keep the spam complaint rate reported in Google’s Postmaster Tools low, below 0.3 percent, with Google recommending staying under 0.1 percent.

Even if your list is far smaller than that, these rules describe what inbox providers consider normal, well-behaved sending. Meeting them is the simplest way to stay out of trouble as your list grows.

Step 2: Protect Your Sender Reputation

Reputation is built one send at a time. Every message that is ignored, deleted unread or marked as spam counts against you. Every open, reply and click counts in your favour.

Only send to people who opted in

Never buy or rent lists, and do not add people just because you have their business card or they once called you. Purchased lists contain old addresses, people who will report you, and sometimes spam traps: addresses that exist only to catch senders with poor list practices. If you need more subscribers, grow the list properly; our guide on how to build an email list walks through it.

Clean the list regularly

• Remove hard bounces immediately. Most email tools do this automatically.
• Identify subscribers who have not opened or clicked in six to twelve months. Send them a short “Do you still want these emails?” message, and remove anyone who does not respond.
• Honour unsubscribes quickly and never re-add those people.

A smaller list of people who read your mail delivers far better than a large list of people who ignore it.

Send consistently

Sudden spikes look suspicious. A business that sends nothing for eight months and then blasts its entire list is more likely to hit spam folders than one that sends a modest message every month. If you are restarting an old list, begin with your most recently engaged contacts and widen gradually.

Step 3: Make the Message Look Like Real Mail

Content filters are smarter than they used to be; a single word like “free” will not doom a message. But some patterns still hurt:

• One big image with little text. Use real text for your message and images as support.
• Misleading subject lines. “Re:” or “Your order” on a promotion gets reported as spam, and it is also prohibited under US commercial email rules.
• Too many links, or link shorteners. Link to your own website, and keep it to the few links that matter.
• Heavy, messy code. Templates copied from a word processor can carry hidden formatting. Use your email tool’s editor or a clean template.
• No plain information. Include your business name, your physical mailing address and a visible unsubscribe link, as the CAN-SPAM Act requires for commercial email.

Write like a person, with one clear purpose per message. If you want ideas for what to send new subscribers, our welcome email sequence guide has a simple four-message plan.

How to Tell If You Have a Deliverability Problem

• Test sends land in spam in your own Gmail or Outlook account.
• Open and click rates drop suddenly across the whole list, not just for one message.
• Customers say they never got an email you know you sent.
• Your email tool shows warnings about authentication, bounces or complaints.
• Google Postmaster Tools, which is free for domain owners, shows a rising spam rate or authentication failures.

You can also view the original headers of a test message in Gmail (“Show original”); it shows whether SPF, DKIM and DMARC passed.

Common Email Blast Mistakes

• Sending from a free webmail address through a marketing tool.
• Adding a second SPF record instead of editing the existing one.
• Setting up DKIM in the email tool but never adding the DNS records.
• Importing every contact from your phone or invoicing system without permission.
• Blasting a long-dormant list all at once.
• Hiding the unsubscribe link, which leads people to click “Report spam” instead.
• Ignoring bounce and complaint reports until a provider starts blocking you.

Email Deliverability Checklist

1. Send from an address on your own domain.
2. Confirm SPF includes your email service, with only one SPF record on the domain.
3. Add the DKIM records your email service provides.
4. Publish a DMARC record and review its reports.
5. Include one-click unsubscribe, your business name and your mailing address.
6. Remove bounces and long-inactive subscribers.
7. Send on a steady schedule rather than occasional large blasts.
8. Test each message in a Gmail and an Outlook inbox before sending to the list.

Domain and DNS settings are where many deliverability problems start and where they are easiest to break. If you would rather have someone keep your domain, DNS records and website in order, see our hosting and maintenance services.