Why Your Business Emails Land in Spam, and How to Check Your Domain in 5 Minutes

A customer calls and says they never got your quote. Another finds your invoice in their spam folder a week later. Someone fills in your contact form, hears nothing back, and goes to a competitor.

An email that goes to spam doesn't bounce back, so you usually never know. Very often the reason is a few missing settings on your domain, and you can check them yourself, for free, in about five minutes.

The Four Settings That Matter

Your domain has a settings page, usually with the company you bought it from or your hosting company. Four small entries there decide how your emails are treated.

• SPF is a list of who is allowed to send email from your domain. For example, Gmail, Outlook or your website's contact form.
• DKIM is like a signature on every email. It shows the email really came from you and wasn't changed on the way.
• DMARC tells Gmail, Outlook and others what to do if an email pretends to be from you. It can also send you a report of who is using your domain to send email.
• MX decides where your incoming email goes. It has nothing to do with sending. If it's missing, other email servers try your website's address instead, which usually can't accept email, so emails to you can be held up for days and then bounce. Some domains have a special "null MX" on purpose, which tells everyone straight away that the domain doesn't receive email. That's different from simply missing.

The first three help your emails get delivered. The fourth helps you receive emails.

Why This Matters More Now

In February 2024, Google and Yahoo made their rules stricter.

Everyone who sends email to Gmail or Yahoo users now needs at least SPF or DKIM, and has to keep spam complaints very low. Companies that send a lot of email (more than 5,000 a day to Gmail) need all three: SPF, DKIM and DMARC. In May 2025, Microsoft did the same for anyone sending more than 5,000 emails a day to Outlook.com, Hotmail and Live addresses. Emails that don't meet the rules can be refused.

Even below 5,000 a day, emails from a domain without these settings are trusted less.

How to Check Your Domain in 5 Minutes

All you need is your domain name. That's the part after the @ in your email address, like yourbusiness.com.

Type it into any of these free checkers:

• Google Admin Toolbox: Check MX. Google's own free checker. Good if you use Gmail for your business (Google Workspace).
• MXToolbox SuperTool. A long-time favourite. You check each setting separately.
• MailSenpai Email DNS Checker. Checks all four settings in one go and explains the results in simple words. The result shows on the page, with no email needed. They also offer a full step-by-step report by email, but to get it you have to agree to receive both the report and their marketing emails.

What the results mean

SPF. You should have only one SPF entry, starting with v=spf1. If you have two, it's broken, even if both look correct. It should include every service that sends email for you. If the checker warns about "too many lookups", the entry has gone over SPF's limit of 10, and SPF stops working with an error, just like having two entries.

DKIM. Each email service stores its DKIM under its own name, called a "selector". Gmail uses "google". Microsoft 365 uses "selector1" and "selector2". A checker can only find DKIM if it looks under the right name. So if it says "DKIM not found", it doesn't always mean you don't have it. Ask whoever set up your email which name they used.

DMARC. If you see p=none, that means "just watch". It's a good, safe start. Later, it can be changed to p=quarantine, which sends fake emails to spam. Also look for rua= followed by an email address. That's where the reports go. Without it, nobody ever sees them.

MX. This should show the email provider you actually use today, such as Google or Microsoft. If it shows an old provider, replies to you might be going missing.

Mistakes We See All the Time

• Two SPF entries. Someone adds a new email tool and creates a second SPF entry instead of editing the first one. The rules say a domain can only have one, so SPF stops working for all your email.
• A forgotten email tool. Your Gmail is fine, but your website's contact form, invoicing software or newsletter tool isn't in SPF, and those emails land in spam. Using Amazon SES? See our Next.js, AWS SES and Netlify guide.
• DMARC set up once and forgotten. It's on p=none for years and nobody reads the reports.
• Old MX after a move. You changed email provider, but the MX still points to the old one.

Green Ticks Don't Mean Your Emails Reach the Inbox

The checkers above only look at your settings. They can't tell you if a real email passes, or lands in the inbox.

So test with a real email. It takes one minute:

1. Send an email from your business address to a personal Gmail address.
2. Open it in Gmail, click the three dots at the top right, and choose Show original.
3. Look at the top. You'll see SPF, DKIM and DMARC, each with PASS or FAIL.

Repeat for each tool that sends your email.

If everything says PASS and it still goes to spam, your settings are fine, but other things also count: how much Gmail trusts your domain and the server it came from, how people react to your emails, and Gmail's own filters (Google explains these here). The email itself matters too: a test that just says "test" can land in spam even from a perfect setup. Click Not spam, send a normal email with a proper subject and a few lines, and reply to it.

For Your Developer: Get Told When Something Breaks

These settings usually break when someone adds a new tool, moves hosting or edits them by hand. Three simple ways to keep an eye on them:

1. Read the DMARC reports. Once rua= has an address, providers such as Google and Yahoo send a report, usually once a day, of who sent email using your domain. A DMARC report service turns them into something readable.

2. Run a quick check on a schedule:

dig +short TXT yourdomain.com                    # SPF
dig +short TXT _dmarc.yourdomain.com             # DMARC
dig +short TXT google._domainkey.yourdomain.com  # DKIM, selector "google"
dig +short MX yourdomain.com                     # MX

3. Use a checker's API. For example, MailSenpai has a free DNS check API that needs no key:

curl "https://app.mailsenpai.com/tools/dns-check?domain=yourdomain.com&lang=en&selector=google"

Change selector= to your own email service's DKIM name. Their documentation says you can run 30 checks an hour from one IP address, and results are saved for 15 minutes (repeat checks in that time don't count). Error 422 means the request itself is wrong, for example the domain is missing, so fix the request rather than retrying it. Error 429 means you've hit the limit, so wait before trying again. Neither means your settings are broken. And test with your own domain, not example.com.

When to Ask for Help

One simple problem, like no DMARC, you can often fix yourself with Google's or Microsoft's help pages. Ask for help if you use several email tools, have two SPF entries, or can't find your DKIM. Good questions for your developer or email provider:

• Which tools send email using our domain, and are they all set up for SPF and DKIM?
• Do we have DMARC, and who reads the reports?
• Does our MX point to the email provider we use today?
• Have you sent a test email from each tool and seen PASS for all three?

Common Questions

Can DMARC stop my own emails?

Not when it's set to p=none, because that only watches. Only make it stricter once the reports show all your tools passing.

My website is on Shopify, Wix or Squarespace. Do I still need this?

Yes, if you send email from your own domain. Your website builder doesn't set these up for your business email or your other email tools.

Sources

• Rules: Google, Yahoo and Microsoft sender requirements
• DKIM selectors: Google Workspace and Microsoft 365
• Standards: SPF (RFC 7208), DMARC (RFC 7489) and null MX (RFC 7505)
• Gmail Help: View the original message
• Checkers: Google Admin Toolbox, MXToolbox, MailSenpai and its DNS check API