Misclassified emails are more than just an annoyance. They’re a costly, time-consuming security risk. Every time a safe email is mistakenly flagged as malicious, productivity grinds to a halt. Employees miss critical messages, IT teams scramble to release them, and frustration mounts. On the flip side, when a truly dangerous email slips through, the consequences can be devastating—leading to breaches, data loss and financial damage.
When security teams can accurately distinguish between malicious, suspicious, spam and graymail, they can reduce risks, minimize disruptions and restore trust in the inbox. Here’s how.
Understanding email classifications: malicious, suspicious or safe
Email security has traditionally relied on binary classifications. Emails are either malicious and quarantined, or they’re safe and delivered to inboxes. However, this oversimplification ignores a critical middle ground—suspicious emails.
Suspicious emails don’t have definitive indicators. Instead, they have characteristics that warrant caution. This middle category is crucial because mishandling these emails can expose organizations to cyber threats. Or they can disrupt business operations because legitimate messages are quarantined.
Proofpoint email classification split up into three categories.
Safe emails: trustworthy communications
Safe emails are legitimate messages that come from known senders and authenticated domains. They contain no indicators of phishing, malware or social engineering attempts. Here are their attributes:
- Sender verification. The sender's domain passes authentication checks (SPF, DKIM, DMARC), confirming that the email is from a trusted source.
- No malicious attachments or links. URLs and attachments are scanned, showing no evidence of malware, trojans or phishing schemes.
- Content legitimacy. The message is free from urgent language or other manipulative tactics, like attempts at financial fraud.
- Behavioral consistency. The sender’s past email behavior aligns with their current email patterns, like a finance team member regularly sending invoices.
Once these emails are verified as safe, they can be confidently delivered to a recipient's inbox. The security team does not need to intervene.
Proofpoint email classification showing safe messages.
Malicious emails: the definite threats
Malicious emails are clear threats that contain harmful payloads or deception tactics. Typically, these emails are quarantined automatically because their risk is evident. Here are their attributes:
- Phishing attempts. These messages are designed to steal credentials. Often, they use fake login pages, deceptive links or impersonation.
- Malware attachments. These files execute malicious code when they are opened.
- Spoofed senders. Attackers often pretend to be trusted contacts, vendors or executives in an effort to manipulate recipients into taking harmful actions.
- Known indicators of compromise (IOCs). The email may match known attack patterns, flagged domains or blacklisted IP addresses.
When emails meet these criteria, security teams can take decisive action—quarantine them, alert users and block associated domains.
Proofpoint email classification showing a malicious email threat.
Suspicious emails: the unclear middle ground
Suspicious emails fall in between safe and malicious. These messages raise red flags but lack definitive proof of being a threat. This ambiguity is why handling them presents a major challenge. They typically include:
- Unusual sender behavior. The email comes from a known contact but is out of character. For example, a CEO suddenly requests a wire transfer from an employee who never handles finance.
- New or unverified domains. The email comes from an unfamiliar domain that isn’t outright malicious but is new or unverified.
- Urgent or manipulative language. The sender pressures the recipient to take immediate action, like: "Act now! Your account will be deactivated in 24 hours!"
- Unscannable attachments or URLs. Some links and attachments evade detection tools, making it hard to determine their safety.
Suspicious emails put security teams in a difficult position. If they automatically quarantine them, this can lead to disruption if it turns out that they are legitimate. However, if these messages are allowed through, then organizations are exposed to potential threats.
Proofpoint email classification showing suspicious emails.
Why suspicious emails are difficult to handle
Unlike malicious emails, which are easy to spot, suspicious emails require deeper scrutiny. Here are the main reasons why handling them is challenging:
1. Balance matters—business disruption vs. security risk
If emails are quarantined indiscriminately, this can lead to false positives. This means that business processes get slowed down because legitimate take longer to arrive. Conversely, if suspicious emails are allowed into inboxes, there’s an increased risk that an employee will fall for a well-crafted phishing attempt. The challenge lies in striking the right balance between security and business continuity.
2. Context matters—only the recipient can truly judge
Some suspicious emails need to be interpreted by humans. For example, a finance team member might recognize a payment request from a known vendor that seems off but is still valid. Automated tools lack this insight.
3. Appearances are deceiving—adaptive attack techniques
Cybercriminals constantly refine their tactics, crafting messages that evade detection by mimicking legitimate business interactions. Often, they use email addresses that are look like a recipient’s known contacts. They also manipulate sender names and embed fraudulent links that look legitimate at first glance.
How organizations should handle suspicious emails
Suspicious emails do not fit neatly into “safe” or “malicious” categories. That’s why organizations need a nuanced approach to handling them.
Email showing a suspicious email pop-up.
1. Implement a suspicious email category in security policies
Rather than forcing a binary choice between inbox delivery and quarantine, security teams should establish a clear protocol for handling suspicious emails. This may include:
- Routing them to a separate "suspicious" quarantine for user review
- Sending alerts to users with guidance on how to inspect the email safely
- Providing an easy way for users to report emails that look like threats
2. Use AI and behavioral analysis
Advanced email security tools now use AI-driven behavioral analysis to identify deviations from normal communication patterns. By examining sender behavior, email context and historical patterns, AI can help refine the classification of suspicious emails.
3. Enable user reporting and training
Security awareness training empowers employees to recognize and report suspicious emails. Here are some tips:
- Encourage users to report emails that seem questionable
- Provide phishing simulations to train users on real-world attack scenarios
- Educate employees on telltale signs of phishing and social engineering threats
Conclusion
Email security cannot rely on simply classifying messages as “safe or malicious.” Suspicious emails are a critical third category that must be handled carefully.
To balance security and business efficiency, you need to adopt a multilayered approach to security. Look for a solution that combines AI-driven detection, user awareness training and adaptive quarantine policies.
If you want to test drive a balanced approach to security, get a demo of Proofpoint Core Email Protection today.
