Why emails go to the spam folder?
Discover why your emails are ending up in spam and how to fix it.
Not seeing emails in your inbox?
If you're not receiving emails as expected, there's a strong chance they’ve been delivered to your spam folder instead.
Even legitimate, carefully crafted emails can occasionally get flagged as spam. When this happens, it can affect your open rates, customer engagement, and campaign performance.
In this guide, we’ll break down the main reasons emails end up in the spam folder and walk through practical steps to help ensure your messages land where they belong—right in the inbox.
How spam filters work
Spam filters are tools used by Internet Service Providers (ISPs) and webmail services to classify incoming emails as either spam or legitimate. Every time you send an email, it passes through these filters before reaching the recipient's inbox. These filters help protect users from unwanted or potentially harmful emails, such as spam or phishing attempts.
The placement of emails, whether they end up in the inbox or the spam folder, is determined by ISPs and webmail providers based on various factors, each with its own criteria. As a result, an email that is flagged as spam on one platform, like Outlook, may not be treated the same way on another, like Gmail or Yahoo.
Reasons why emails end up in spam
Sender reputation
Sender reputation refers to how inbox providers assess your credibility as a sender. It plays a key role in how your emails are delivered and sorted. A poor sender reputation can result in your emails being sent directly to the spam folder by inbox providers.
When inbox providers determine the sender reputation for each domain or IP, each provider evaluates various metrics. Some of the main metrics that contribute to the score include:
Open rate
Percentage of recipients who have opened an email out of the total number of emails delivered.
Click rate
Percentage of recipients who have clicked a link in an email out of the total number of emails delivered.
Hard bounce rate
Percentage of email deliveries that failed due to a permanent issue (e.g., invalid email addresses).
Soft bounce rate
Percentage of email deliveries that were rejected due to a temporary issue (e.g., the recipient's inbox being full).
Spam/Complaint rate
Percentage of recipients who marked your email as spam out of the total number of emails delivered.
Unsubscribe rate
Percentage of recipients who have unsubscribed from a campaign using the unsubscription link out of the total number of emails delivered.
High hard bounce (above 2%), unsubscription (above 1%), or complaint (above 0,2%) rates can lead to an account or email campaign suspension.
🧑💻 Your sending IP has a bad reputation
Your sending IP plays a critical role in deliverability. A poor IP reputation, due to high spam complaints or bounces, can significantly hurt your email performance. If you're using a shared IP, your reputation depends on the actions of all users on that IP. A dedicated IP ensures more control, but you must still maintain a good reputation.
Check your IP reputation using tools like MultiRBL to see if your IP is on any blocklists.
Reach out to your ESP if you're experiencing IP reputation issues for further insights.
🌐 Your domain has a bad reputation
Your domain’s reputation also impacts deliverability, especially as spam filters weigh domain history heavily. If your domain is associated with spammy activity, your emails are more likely to land in the spam folder.
Check your domain reputation with tools like Gmail’s Postmaster or MXToolBox.
Check if your domain is on a blocklist using services like MultiRBL or MXToolBox to ensure it's not flagged.
📝 Your IP address or domain has been blocklisted
If your emails are landing in the spam folder, your IP address or domain may be blocklisted by an ISP or anti-spam service. This often happens when your emails are flagged for suspicious activities like spamming or phishing.
🆓 You are using a free email address
Free email addresses are great for personal communication but using them for business emails can get your messages flagged as spam. A professional email address boosts credibility and increases the chances of reaching the inbox.
👎 Your contacts are not engaging with your emails
ISPs track how recipients engage with your emails. Low engagement (such as emails not being opened or clicked) can signal to spam filters that your emails are irrelevant, which may lead to them being marked as spam. Keep your contact list updated and send relevant, engaging content.
🎯 You aren’t targeting the right contacts
It’s important to send emails to recipients who are genuinely interested in your content. Rather than emailing your entire list, segment your audience based on past behavior or interests to increase relevance and engagement, improving deliverability.
❌ Your contacts have not consented to receive your emails
Always ensure you have permission before sending emails. Buying or renting email lists can result in your emails being flagged as spam and may violate platform terms. Non-consensual emails often lead to complaints and poor deliverability.
🧹 You haven’t cleaned your contact list
An outdated or inaccurate contact list can increase bounce rates and spam complaints. Regularly clean your list to remove invalid or inactive email addresses, ensuring you're only sending to engaged, legitimate recipients.
🗑️ Your recipients marked your emails as spam
If your emails are marked as spam by recipients, ISPs may start filtering your emails into the spam folder automatically. Make sure your emails provide value and are expected by your subscribers, so they’re more likely to engage and not report them as spam.
🔥 You didn’t warm up your dedicated IP address properly
ISPs and email providers closely monitor sender behavior to prevent spam and ensure legitimate emails reach inboxes. Starting with a new dedicated IP or after a long period of inactivity means you have a "cold" reputation. This makes ISPs watch your email activity closely. Warming up your IP gradually is essential to building a positive sender reputation and reducing the chances of your emails being marked as spam.
📮 You don’t have a working reply-to address set up
It’s important to specify a reply-to address in your emails, avoiding “[email protected].” Spam filters often flag no-reply addresses as suspicious, increasing the chance your emails will be marked as spam.
Using a no-reply address also creates a poor experience for recipients, as it prevents communication. If you don’t want replies, set up a monitored mailbox to avoid missing important inquiries.
Remember, the reputation of your reply-to address matters. Suspicious or free email domains can also lead to your emails being flagged as spam.
📝 Explore the guide on how to set up a reply-to email here: Create an email template
Email content
⚠️ Your email contains "spam trigger" words
Your emails can easily be marked as spam if the subject line appears overly promotional or suspicious. Certain words, styles, and formatting choices are known to trigger spam filters, so it’s essential to be mindful of how you write your subject lines. Try to avoid using full uppercase text, most recipients prefer lowercase, and subject lines written entirely in caps are often treated as spam indicators. The same applies to excessive punctuation, such as long strings of exclamation marks or decorative symbols. Other red flags include:
Writing SUBJECT LINES IN ALL CAPS
Filling your subject with symbols like “!!!!!” or “***”
Relying on a single large image in the body of your email
Using aggressive, hype-driven phrases such as:
“LIMITED TIME OFFER!”
“100% FREE”
“ACT NOW”
Remove any spammy words or phrases in your email copy, subject line, or preview text.
Keep your copy concise and meaningful. If you don’t, content filters might mistakenly classify it as “spoetry”, that’s randomly generated copy that spammers use to trick receivers into thinking there’s real content in their emails. Spam filters have become better at spotting this gibberish, but they sometimes generate false positives.
🖼️ Your email is image-only
Sending an email that contains only one image can hurt your deliverability because inbox providers often see image-only messages as suspicious. Instead of using a single large graphic, create emails that include both text and images. Large image files can also trigger spam filters. Since spammers often hide content inside images, modern filters pay extra attention to emails with very little text.
To avoid this, try adding at least 500 characters of text, such as your company address, contact details, legal notes, or an unsubscribe link. Also remember to include alt text so your message is still understandable if the image doesn’t load.
📝 Read more about content blocks in email template editor: Content blocks
🔗 You are overusing URL shorteners and links
Shortened URLs can negatively impact your email deliverability because spammers often use services like bit.ly to hide the true destination of their links. To maintain trust with inbox providers, use full, transparent URLs and ensure the link your users see actually leads to the correct page, without unexpected redirects. For the clickable text, simple options like “click here,” short descriptive labels, or clear buttons work best.
Including too many hyperlinks can also raise flags with spam filters. Spammers commonly pack their emails with excessive links, both hidden and visible. While a few legitimate links won’t cause issues, limit them to what’s truly necessary, especially if any link directs to a domain other than your own.
💌 Your email isn't personalized for each customer
Personalizing your emails increases the chances that email clients will recognize them as important, making it more likely that subscribers will open them. When an email client sees that you know the recipient, it significantly reduces the risk of your email being flagged as spam. You can use variables to personalize email configurations in XFlow.
📝 Learn more about personalizing emails with variables: Add variables for personalized emails
If you're unsure, test your email templates with free spam filter tools like Mail Tester to identify potential issues that could cause your emails to be flagged.
📬 Make unsubscribing easier with two links or buttons
Including an unsubscribe link at both the top and bottom of your emails is a good practice. Allowing recipients to easily opt out when they no longer wish to receive your emails can help reduce spam complaints and improve your open rates as you send to a more engaged audience. While you want to avoid high unsubscribe rates, it's better for someone to unsubscribe than mark your email as spam. This also helps in cases where emails get clipped due to their size, ensuring that users can still opt out easily.
📝 Learn how to use unsubscribe links in your emails: Add variables for personalized emails
Email authentication
🔓 Your email is not fully authenticated
Emails often land in spam when your domain isn’t properly authenticated, because ISPs and mail providers can’t confirm that your messages are legitimate. To establish trust, your domain can use the key email authentication standards: SPF, DKIM, and DMARC, which work together to verify sender identity and prevent spoofing.
For full DMARC compliance, you’ll also need a branded sending domain (DSD) whose root domain matches the root domain of your “from” address. For example, if you send from [email protected], your authenticated sending domain should be something like send.example.com.
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