Temp mail detection has improved, but abuse hasn’t slowed. One reason is email forwarders. Unlike classic disposable inboxes, forwarders redirect mail to a real, persistent inbox and often without leaving obvious traces. Services like Cloudflare’s Email Routing make it easy to generate infinite aliases under a single domain, each one capable of sidestepping blacklist-based filters.
What even is a forwarder, anyway?
An email forwarder is a service that receives email sent to one address and transparently redirects it to another. Unlike temporary email services, which typically host disposable inboxes with limited lifespans, forwarders don’t store mail. Instead they simply route it. The original sender often has no idea forwarding is occurring. These services are often used for privacy, custom domains, or aliasing, but in abuse contexts, they act as cloaking layers, obscuring the real destination mailbox. Forwarders can make throwaway email addresses appear stable and legitimate, which is why they evade basic temp mail detection strategies that rely on known disposable domains or MX patterns.
Why they don’t look like temp mail (but kind of are)
Forwarders don’t exhibit the usual traits of temp mail. Indeed they look reputable, maintain consistent MX records, and route mail to long-lived inboxes. From the outside, they look stable, legitimate addresses. But functionally, they’re disposable. A user can create dozens of unique forwarding aliases, discard them at will, and retain inbox continuity, all without touching a traditional temp mail provider. This blurs the line between legitimate email forwarding and intentional obfuscation. Detection systems that rely on domain reputation or short inbox lifespans miss this entirely, or struggle to classify, making forwarders a stealthier form of temporary email.
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The Cloudflare and .Co problem
Cloudflare Email Routing has made email forwarding accessible at scale. Users can create unlimited forwarding addresses on their own domains, with minimal setup. Since these domains often have no public association with Cloudflare, traditional detection methods-like filtering based on known disposable or forwarding domains-fail. The routed emails appear to come from unique, custom addresses with clean reputations, bypassing blocklists and heuristic filters. Attackers exploit this to generate bulk high trust aliases, using Cloudflare’s infrastructure as a shield. The scale, stability, and low visibility of these forwarders make them ideal for evading temp mail detection.
By offering a simple developer friendly IaaS solution, CloudFlare and other providers offer developers a friendly alternative to hosting and managing systems, which was previously a barrier to entry for many providers. This new and simplied approach makes it harder to catch. Not not impossible.
How forwarders slip past most filters
Many filters detect disposable email addresses using static blocklists, disposable domain patterns, or heuristic signals. Forwarders, however, bypass these by design. They often use well-configured custom domains with long histories, consistent DNS setups, and no ties to known disposable services. Since they don’t host inboxes, there’s no telltale webmail interface or inbox expiry to trace. Forwarded domains inherit the infrastructure setup reliability, further reducing noise in detection signals. The end result is that forwarders hide well as legitimate email addresses, getting past systems that rely on shallow metadata or domain reputation alone.
The line between privacy and abuse
Forwarders serve multiple roles, both as a privacy tool and an abuse vector.
For privacy conscious users, they offer protection against spam, phishing, and unwanted tracking. Users can rotate aliases, limit exposure, and maintain control over inbound communication as well as maintain anonymity.
But the same features that we enjoy such as address rotation, domain obfuscation, inbox redirection are also exploited by fraud singups and account farming. Abuse doesn’t come from the technology itself but rather from the scale and intent.
This ambiguity complicates detection: blocking all forwarders punishes legitimate users, while allowing them unlimited access absolutely enables high volume abuse - which we’ve seen first hand from our own analysis. So where do you draw the line? That’s a tough call to make.
Our analysis reveals rapid growth in abuse linked to email forwarders, especially those powered by IaaS email routing providers. Attackers create catch all emails on low-cost domains (commonly cheap and ccTLDs such as .edu.pl, .top .xyz), cycling them to bypass rate limits and blacklists. These aliases allow mass account creation and free trial abuse. Abuse patterns show clustering around newly registered domains, often in rapid succession and often with other evasion techniques such as rotating IPs. Detection gaps enable sustained, large-scale exploitation of forwarders as a core vector in email-based abuse if not stopped quickly.
How Temp Mail Detector handles forwarders
We obviosuly can’t go into too much detail here, but Temp Mail Detector makes use of various signals and heuristics far beyond basic domain blocklists to identify forwarders. We analyses many different signals, check for forwarder infrastructure, and monitor behavioural signals for abuse. The system also makes use of real time feedback loops to stay one step ahead.
Stopping forwarder abuse as well as regular disposable email abuse requires layered detection. Relying solely on domain reputation is not enough, and static block lists will only get you so far. By integrating with real time APIs such as ours for ongoing validation, you keep up with new forwarding abuse and domains, allowing you to focus on what you know and do best - your business.