Common reasons emails may land in the spam folder

Sooner or later, it happens to everyone: an email lands in spam instead of the inbox. Mailbox providers like Gmail, Outlook, and Yahoo don't share the exact rules behind their spam filters, so there's no way to prepare for every scenario. But a handful of common causes explain most spam folder issues, and each one has a fix.

The most important rule in email marketing: only send to people who gave you clear consent. Never assume someone wants to hear from you just because you have their email address.

How to get consent:

Use clear, transparent language on your sign-up forms. Let people know they're joining your email list and what kind of emails to expect. For example:

"Sign up for my email list and grab your copy of [lead magnet]. Your information is 100% secure and will never be shared. By signing up, you'll be added to my list, where I share [frequency] [topic]. You can unsubscribe at any time."

For an extra layer of assurance, Flodesk forms include an optional marketing consent checkbox, which requires subscribers to actively check a box agreeing to receive marketing emails before they can sign up. This can also help with privacy regulations like GDPR. Learn how to collect explicit marketing consent.

Why this matters:
If subscribers don't recognize your emails, they're far more likely to mark them as spam. And that doesn't just affect the one subscriber who complained: inbox providers weigh complaints against your entire sending domain, which can affect deliverability for everyone on your list.

Spam filters track how subscribers interact with your emails. Low or dropping engagement signals to inbox providers that people don't want your content, which can push future sends toward spam.

Positive engagement signals include when subscribers:

• Open your emails

• Click links inside your emails

• Move your email out of the spam folder

• Add your email address to their Contacts or Address list

• Reply to your email

• Forward your email to someone else

Recency matters more than history here. A subscriber who was highly engaged for years but has gone quiet for the last six months is riskier for your sender reputation than someone who joined last month and has opened a couple of emails. Inbox providers weigh recent activity more heavily than past loyalty.

How to check engagement in Flodesk:
On your Emails dashboard, hover over a sent email's card and click View results. You'll see open rate, click rate, unique opens and clicks, deliverability, unsubscribes, and bounces.

Improve engagement through list cleaning:
Regularly remove or archive unengaged subscribers from your active list. A good starting point: filter for subscribers who haven't opened or clicked in the last 90-180 days, move them to a separate segment, and exclude that segment from future sends.
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Every marketing email needs a visible, working unsubscribe link. It's a legal requirement, and it's also good for your deliverability.

If subscribers can't find a way to opt out, they'll often mark your email as spam instead, which is far more damaging to your sender reputation than a simple unsubscribe.

Flodesk automatically includes a one-click unsubscribe link in every email, so this part is handled for you. Just make sure the footer text is legible (check your font size and color) so subscribers can actually see it.

You can see how you're doing with marked-as-spam complaints in the spam rate table on your Emails Analytics dashboard. If you connect Google Postmaster Tools, Gmail's own data will surface there too, since Gmail doesn't report spam complaints back to Flodesk directly.

Design plays an important role in email marketing, but text matters just as much. If your email is made up of only images, subscribers with connection issues may see a blank email with no context. Spam filters also read text more easily than images, and scammers often lean on image-heavy emails to avoid text-based filters.

This doesn't mean you should avoid images. It means your emails shouldn't rely on images alone. Note that Layout blocks, even ones that only contain text, render as static images in the final email. Balance these with standard text blocks so your email stays both branded and functional, and add alt text to your images and layout blocks so the content still comes through if images don't load.

Certain words and phrases get flagged more often because scammers and phishing emails misuse them. Review your subject lines and body copy for language that could raise a red flag, and test your emails before sending to your full list.

Two easy ways to test:

• Use a free tool like Mail-Tester to score your email's spam likelihood

• Send a test email to yourself from the Flodesk editor: click the paper plane icon, add a subject line and your own email as the recipient, then click Send test now

If your test lands in spam, revisit your subject line, copy, or design before sending it out.

Sending marketing emails from a free address (Gmail, Yahoo, Hotmail, iCloud, and similar) makes you far more likely to be flagged as spam. Google and Yahoo formalized requirements in 2024 that bulk senders use a custom domain, and it's one of the first things spam filters check.

The fix: use a custom domain email (like hello@yourbrand.com) and authenticate that domain. Authentication tells inbox providers you're really you, using three records:

• SPF: confirms Flodesk is authorized to send on your domain's behalf

• DKIM: adds a digital signature so providers can verify your emails haven't been tampered with

• DMARC: tells providers what to do if an email fails SPF or DKIM, and gives you reporting to catch spoofing

Authentication can drift over time if something changes on your domain provider's end, so it's worth double-checking your setup periodically under Account settings > Domain setup, even if it's worked before.

Once your domain is authenticated, warm it up gradually rather than sending a large volume right away. A brand-new domain that suddenly sends a high volume of email looks like a spam flag to inbox providers, even with authentication in place.
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Two link issues can hurt deliverability:

HTTP instead of HTTPS. HTTPS encrypts data between your subscriber's browser and the website, while HTTP sends it in plain text. Spam filters treat HTTP links as less trustworthy, and browsers often flag HTTP sites as "not secure." Always use HTTPS links, including for your website and social links under Account settings > Branding.

Shortened or redirect-based links. Links that redirect through another service, like Bitly, TinyURL, shortened YouTube links (youtu.be), or Amazon's shortened links (amzn.to), are increasingly flagged by inbox providers and tend to see a noticeable drop in open rates. These are just a few examples: any link that hides its true destination behind a redirect can raise the same flag. Instead, copy the full URL directly from your browser's address bar (for a YouTube video, open it in your browser rather than using the share link).

If you've gone quiet for a while and then send a big campaign to your entire list, that spike can look suspicious to inbox providers, sometimes resembling an account takeover. The same applies when you switch platforms or authenticate a new domain: you're treated as a new sender and have to rebuild trust, regardless of your sending history elsewhere.

The fix: warm up gradually. Start with your most engaged subscribers, increase your volume over a few weeks, and let your sender reputation build before sending to your full list. Consistency matters too: domains tend to go cold after four to six weeks of inactivity, so sending at least monthly helps maintain the trust you've built.

Landing in spam once in a while isn't something to worry about. But if it's happening often, work through this checklist:

• Get clear consent before adding anyone to your list (consider enabling the marketing consent checkbox)

• Send relevant, expected content, and personalize where you can

• Keep your unsubscribe link visible and legible

• Use more text than images in your email design, and add alt text to images and layout blocks

• Watch for spam trigger words in your subject line and body

• Send from an authenticated custom domain, not a free email address, and warm it up gradually

• Use full HTTPS links instead of shortened or redirect-based links

• Warm up your sending gradually after any gap, platform change, or new domain authentication

• Check your spam rate table in Emails Analytics, and connect Google Postmaster Tools to see Gmail's data alongside it

Why did my email land in spam if my subscribers opted in?
Opt-in reduces the risk significantly but doesn't guarantee inbox placement. Design, links, authentication, and ongoing engagement all play a role too.

Does one spam complaint hurt my sender reputation?
Not on its own. Occasional complaints are normal. What matters is your complaint rate trending upward over time.

Does switching my sending domain fix a spam problem?
Not by itself. A new domain starts with no reputation at all, which can create its own deliverability issues. Cleaning your list and improving engagement is usually a better first step than switching domains.