Why Your Emails Go to Spam (and How to Fix It)

"Check your junk folder" has quietly become part of doing business, and it shouldn't be. When your quotes, invoices and replies land in spam, you lose deals without ever knowing they existed. Here are the real reasons business email goes to junk, roughly in order of how often we find them, and the fix for each.

1. Missing or broken authentication

The most common cause by a distance. If your domain lacks proper SPF, DKIM and DMARC records, receiving servers can't verify your email is really from you, and since the Google, Yahoo and Microsoft crackdowns that began in 2024, unverified mail is treated harshly by default. The classic symptoms: mail to Gmail addresses junks more than mail to anyone else, and it got worse without you changing anything.

Fix: set up all three records properly and move DMARC to enforcement. Plain English explanations are in SPF, DKIM and DMARC Explained, and the Microsoft 365 walkthrough is in our DMARC setup guide.

2. Unauthorised senders damaging your domain

Every tool that sends email as your domain without being authorised in your SPF/DKIM setup generates failing mail, and a steady stream of failures erodes how receiving servers score your whole domain. Most businesses have several of these and don't know it. Worse, if criminals are spoofing your domain, their junk gets counted against your reputation too. DMARC reports are the only way to see either happening; our DMARC guide explains what they reveal.

Fix: publish DMARC, read the reports, authorise the legitimate senders and enforce against the rest.

3. Sender reputation and list hygiene

Providers track how recipients treat your mail. High bounce rates from stale address lists, spam complaints, sudden volume spikes and low engagement all mark your domain down. A newly registered domain sending 500 emails on day one looks like a spammer even when it isn't.

Fix: clean your lists, remove hard bounces immediately, warm up new domains gradually, and never buy email lists. If you send marketing email, keep it on a subdomain so a campaign misstep can't sink your day-to-day business mail.

4. Content that trips filters

Less decisive than people think, but real at the margins: link shorteners, attachment-heavy emails to new contacts, ALL CAPS subject lines, and single-image emails with no text. Filters also learn per recipient, so a contact who once junked your newsletter will keep seeing you in junk.

Fix: write like a human, keep a sensible text-to-image ratio, and send attachments via a link when contacting someone new.

5. Shared infrastructure you don't control

If your email rides on a shared IP (common with some hosting-bundled email and cheaper marketing platforms), another customer's bad behaviour can drag your delivery down with theirs.

Fix: send business mail through a reputable platform like Microsoft 365, and check whether your marketing platform offers better sending options.

How to diagnose your own domain in five minutes

• Send a test email to a Gmail address, open it, choose "Show original", and read the SPF, DKIM and DMARC verdicts at the top.
• Check your DMARC policy: none, quarantine or reject? If it's none or missing, start there.
• Ask your team and your customers whether replies from you have ever appeared in junk. The answer is usually yes more often than anyone expected.

The permanent fix

Points 1 and 2 cause most of the pain and share one solution: full email authentication taken to enforcement and kept there. That is precisely what Flo Verified Mail delivers as a managed service: setup done for you, reports checked every day, your domain taken to full protection so your email arrives and nobody else can send as you. For the complete picture, read our business email deliverability guide.