Why am I suddenly seeing a flood of emails from cloudflare-email.net?
Michael Ko
Co-founder & CEO, Suped
Published 6 Jun 2025
Updated 17 Aug 2025
7 min read
Recently, many email users and administrators have observed a sudden surge of emails originating from cloudflare-email.net. This can be quite alarming, especially when these emails appear unsolicited or suspicious, immediately raising concerns about spam or even a potential attack. It's natural to wonder why this domain, which might seem new or unfamiliar, is suddenly a prominent source of incoming mail.
This phenomenon is largely linked to Cloudflare's Email Routing service. While cloudflare-email.net itself is a legitimate part of this service, its appearance as an SMTP server domain for forwarded emails can be confusing. It can also be indicative of broader issues, ranging from misconfigurations to actual abuse by spammers leveraging the service for their malicious campaigns.
Understanding the nature of these emails is crucial for maintaining your inbox security and overall email deliverability. This guide will help you decipher why these emails are appearing and what steps you can take to protect yourself and your domain.
Understanding Cloudflare email routing and its impact
Cloudflare Email Routing is a service that allows domain owners to create custom email addresses for their domain (e.g., info@yourdomain.com) and automatically forward incoming mail to an existing mailbox, such as a Gmail or Outlook address. This means cloudflare-email.net acts as the intermediary server, delivering the email to your final destination.
When you see a flood of emails from this domain, it suggests that a high volume of mail is passing through Cloudflare's routing system. This could be due to a legitimate increase in traffic to domains using Cloudflare's service, or it could indicate that the service is being exploited. The fact that this is a relatively new domain for email routing (at the time of the observations) can also contribute to suspicion, as new sending domains often face stricter scrutiny from email providers.
Receiving a sudden influx of emails, especially if they are unwanted, can affect your email deliverability. For instance, if these emails are being forwarded to your Gmail account, Gmail might mark them as spam due to their volume or content. Similarly, Outlook and Hotmail filters could also be triggered, causing delivery issues even for legitimate mail.
Why you might be seeing this flood
Several factors can contribute to a sudden flood of emails from cloudflare-email.net. One common reason is simply a legitimate increase in traffic to a website or service that uses Cloudflare's email routing. If a popular service begins using Cloudflare for its email forwarding, you might see more emails from this domain. Another scenario involves email bombing or subscription bombing attacks, where malicious actors flood an inbox with a high volume of messages to overwhelm it or hide other malicious activities.
Poor domain reputation or a lack of proper email authentication can also play a role. If a domain using Cloudflare Email Routing has a low sender reputation or is missing crucial DNS records like SPF, DKIM, and DMARC, even legitimate emails can be flagged as spam by recipient servers. This can result in emails being rejected or landing in the junk folder, contributing to the perception of unwanted emails.
It's also possible that spammers are actively trying to abuse email routing services. These services, by nature, can sometimes mask the true origin of a spam campaign, making it harder for anti-spam measures to trace and block the source. If a service offers blind forwarding that anonymizes sender information, it can inadvertently become a tool for malicious actors, leading to an increased volume of spam from their infrastructure. This can cause you to receive bounce messages for emails you didn't send if your domain is being spoofed.
Subscription bombing attacks
Email bombing, also known as subscription bombing, is a type of attack where a victim's email address is subscribed to a large number of mailing lists or services, often without their consent. This leads to a flood of confirmation emails and newsletters, overwhelming the inbox. Attackers use this tactic for various reasons, including distracting the victim from more serious security breaches or simply causing annoyance. Cloudflare's email routing service, if misconfigured or abused, could inadvertently facilitate such attacks, leading to an increase in unwanted emails originating from cloudflare-email.net.
To identify if you're a target, look for numerous subscription confirmation requests, or if you're seeing strange signups to your newsletter. Implementing CAPTCHAs on sign-up forms and monitoring email logs for unusual activity can help mitigate these attacks.
Identifying legitimate vs. malicious traffic
Distinguishing between legitimate and malicious emails from cloudflare-email.net requires careful examination. The most effective way is to analyze the email headers. Even when an email is routed through Cloudflare, the original DKIM signatures often remain intact, allowing you to trace the true sending domain. If the DKIM aligns with the stated sender in the From address, it's likely legitimate.
However, if the content is unsolicited, suspicious, or clearly spam, despite passing through cloudflare-email.net, it indicates abuse. Reporting such incidents is crucial, but it can be challenging with services that prioritize user privacy or blind forwarding. Cloudflare does provide a postmaster page and guidance on reporting abuse, which is a good starting point.
Expected content: The email is something you signed up for or were expecting (e.g., newsletter, notification, password reset).
Valid sender: The From address is recognizable and corresponds to a service you use.
Proper authentication: Email headers show passed SPF, DKIM, and DMARC for the original sending domain.
Actions for legitimate email
Monitor: Keep an eye on the volume and content to ensure it remains legitimate.
Whitelist: If necessary, add the sender to your safe list.
Malicious email characteristics
Unsolicited content: Emails are unexpected, irrelevant, or clearly spam.
Suspicious sender: The From address is spoofed or unrecognized, despite the cloudflare-email.net routing.
Missing authentication:SPF, DKIM, or DMARC failures for the alleged sender domain.
Actions for malicious email
Report: Use your email client's spam reporting features and consider reporting to Cloudflare's abuse team.
Block: Block the sender in your email client if the volume is high.
Review security: Check for any unauthorized subscriptions or account activity.
Protecting your inbox and domain
To protect your inbox and domain from unwanted emails, whether they come from cloudflare-email.net or anywhere else, implementing robust email authentication is paramount. DMARC, SPF, and DKIM provide a strong defense against email spoofing and phishing attempts. By properly configuring these records, you inform recipient servers that emails claiming to be from your domain are indeed authorized, reducing the likelihood of them being marked as spam or blocked (blacklisted).
Beyond technical configurations, it's vital to maintain a healthy email sending reputation. This involves consistently sending valuable, wanted emails to engaged subscribers, avoiding spam traps, and promptly handling any spam complaints. Regular monitoring of your domain's sending reputation through tools like Google Postmaster Tools can give you insights into how email providers view your email practices.
If you suspect your domain is being used for unauthorized email, especially via services like Cloudflare Email Routing, consider implementing a DMARC monitoring solution with a p=reject policy. This instructs recipient servers to reject emails that fail DMARC authentication, thereby preventing fraudulent emails from reaching inboxes. Our blocklist monitoring can also help you identify if your domain or IP has been added to any spam blacklists (or blocklists).
Example DMARC record
A DMARC record is a TXT record published in your DNS that dictates how recipient mail servers should handle emails that fail SPF or DKIM alignment. Here's a basic example of a DMARC record with a p=none policy (monitoring mode) and a reporting address:
This record allows you to gather reports on your email traffic and identify potential abuse without impacting email delivery. For a detailed breakdown, refer to our guide on simple DMARC examples.
Authentication Method
Purpose
Impact on deliverability
SPF (Sender Policy Framework)
Authenticates the sending IP address against a list of authorized servers for a domain.
Helps prevent direct domain spoofing; a critical foundation for good deliverability.
DKIM (DomainKeys Identified Mail)
Adds a digital signature to emails, verifying that the email content hasn't been tampered with in transit and the sender is legitimate.
Enhances trust and reduces the chance of emails being marked as spam or blocklisted (blacklisted).
Builds on SPF and DKIM, allowing domain owners to specify how unauthenticated emails should be handled and receive reports on authentication failures.
Provides control over email authentication enforcement and visibility into email abuse, significantly improving inbox placement.
Best practices for email security
Implement DMARC, SPF, and DKIM: Ensure these are correctly configured for your domains to prevent spoofing. Check out our simple guide to DMARC, SPF, and DKIM.
Monitor your DMARC reports: Regularly review DMARC aggregate reports to identify unauthorized sending activity from your domain.
Use strong spam filters: Configure your email client or server to filter out suspicious emails effectively.
Educate users: Teach recipients how to identify phishing attempts and suspicious emails.
Views from the trenches
Best practices
Maintain strong email authentication (DMARC, SPF, DKIM) for your domain.
Regularly monitor your email logs and DMARC reports for unusual activity.
Common pitfalls
Ignoring a sudden increase in emails from unfamiliar forwarding services.
Not having a DMARC policy in place to handle unauthenticated emails.
Expert tips
Consider a 'p=reject' DMARC policy if you want to aggressively block unauthorized emails.
Be aware that some email forwarding services prioritize user privacy, which can complicate abuse reporting.
Marketer view
Marketer from Email Geeks says they observed a sudden flood of mail from cloudflare-email.net as an SMTP server domain and noted it was a new domain.
2024-04-01 - Email Geeks
Marketer view
Marketer from Email Geeks says they also saw this traffic, though not in huge volumes, but enough to be noticeable.
2024-04-01 - Email Geeks
Moving forward
A sudden influx of emails from cloudflare-email.net can be unsettling, but by understanding the underlying mechanisms of Cloudflare Email Routing and adopting robust email security practices, you can effectively manage and mitigate the risks. Prioritizing proper email authentication and diligently monitoring your domain's reputation are key to ensuring email deliverability and thwarting malicious activities.
Cloudflare Email Routing is a service that allows domain owners to create custom email addresses for their domain (e.g., info@yourdomain.com) and automatically forward incoming mail to an existing mailbox, such as a 
Gmail or 
Outlook address. This means cloudflare-email.net acts as the intermediary server, delivering the email to your final destination.
