Phishing emails are fraudulent messages that impersonate a trusted person, company, or service to trick recipients into revealing credentials, payment details, or other sensitive information, or into opening a harmful link or attachment. In email sending, phishing matters because criminals can misuse your domain or brand identity, erode recipient trust, trigger spam complaints, and hurt legitimate campaign performance.

What are phishing emails?

Phishing is a form of social engineering: an attacker uses a believable message, identity, and call to action to influence a recipient’s behavior. The message may claim that an account is locked, an invoice is overdue, a document needs review, a package cannot be delivered, or a manager needs an urgent payment. The goal is usually to steal information, obtain money, install malicious software, or gain access to a business system.

A phishing email does not need to come from your actual email infrastructure to harm your business. An attacker can register a lookalike domain, spoof a visible sender identity, compromise a real mailbox, or copy your design language and transactional messages. To the recipient, the distinction between a genuine account notification and a well-made impersonation attempt may be difficult to see.

For legitimate senders, phishing is both a security issue and a deliverability issue. Security teams care about preventing account compromise and fraud. Marketing, lifecycle, and product teams care because recipients who associate a brand with suspicious mail become less likely to open, click, or trust future messages. Mailbox providers also use many signals to protect users from impersonation and abuse, so poorly authenticated or confusing mail can face greater scrutiny.

It is important to separate phishing from ordinary spam. Spam is unwanted bulk mail, often promotional, that may be annoying but not necessarily deceptive. Phishing is intentionally deceptive and seeks a harmful action. A message can be both spam and phishing, but a consent-based product update can still look phish-like if the sender identity, links, or request are unfamiliar.

Why phishing emails matter for deliverability

Deliverability is not simply whether an SMTP server accepts a message. It includes whether the message reaches the inbox, lands in spam, is rejected, is delayed, or is filtered into a warning view. Phishing concerns affect each of those outcomes because mailbox providers are trying to distinguish legitimate mail from malicious impersonation.

Recipient trust is a deliverability signal

Recipients are part of the filtering system. When people mark a message as spam, report it as phishing, delete it without reading, or avoid clicking because it feels suspicious, those behaviors can reduce the effectiveness of future mail. A sender may have technically valid authentication and still lose trust through confusing content, a surprising request, or inconsistent branding.

For example, imagine a software company normally sends account alerts from notify@example.com, but a new campaign arrives from team@example-mail.co and asks customers to enter a password on an unfamiliar landing page. Even if the campaign is legitimate, the mismatch creates the same uncertainty that phishing attempts exploit. Lower opens, fewer clicks, more complaints, and increased support tickets can follow.

Brand impersonation has indirect costs

When criminals impersonate your organization, the immediate victims may be recipients, partners, or employees. The indirect costs can spread much further:

Customers may ignore genuine password resets, invoices, or security alerts.
Support teams may need to investigate screenshots, links, and sender addresses.
Sales and account teams may have to reassure prospects and customers.
Security teams may spend time monitoring fraudulent domains and compromised accounts.
Legitimate email programs can experience more skepticism, complaints, and unsubscribe requests.

A phishing incident can therefore reduce campaign performance even when the malicious email never passed through your sending provider. The brand damage changes how recipients interpret every subsequent message.

Authentication supports legitimate delivery

Email authentication does not make a message inherently safe, but it helps receiving systems determine whether a sender is authorized to use a domain. SPF identifies which sending hosts are permitted to send mail for a domain. DKIM adds a cryptographic signature that receivers can verify. DMARC connects authentication with the visible From domain and publishes a policy for handling mail that fails the required checks.

Google’s sender guidance requires all senders to Gmail accounts to use SPF or DKIM, while bulk senders have additional SPF, DKIM, and DMARC requirements. Authentication helps protect recipients from spoofing and phishing, while helping legitimate senders establish a more recognizable and verifiable identity.

The practical implication is straightforward: a sender that has not fully authenticated its domains is not only leaving room for spoofing. It may also be making it harder for mailbox providers to reliably distinguish legitimate mail from deceptive mail using the same brand identity.

Phishing is not a standard email metric

Unlike bounce rate, open rate, or complaint rate, phishing is not one universal metric with a single industry formula. It is a category of malicious activity. A sender can, however, measure phishing-related indicators to understand exposure, recipient harm, and the health of its email identity.

Useful operational measures include:

Reported phishing count: the number of recipient, employee, mailbox-provider, or security-vendor reports tied to a message or impersonation campaign.
Phishing report rate: reports divided by delivered messages for a defined campaign or period.
Domain impersonation count: the number of discovered lookalike domains, fraudulent subdomains, or unauthorized services using your brand.
DMARC failure volume: mail claiming to use your domain that fails DMARC evaluation, especially traffic from unknown sources.
Compromised mailbox count: the number of real employee or shared mailboxes used to send malicious content.
Phishing-related support contacts: tickets about suspicious email, fake login pages, invoice fraud, or account-verification requests.

None of these measurements alone proves that your sender reputation is damaged. A DMARC failure, for instance, can be caused by a legitimate service that was not included in your authentication setup. The value comes from trend analysis, source investigation, and correlating the data with complaints, authentication results, and recipient reports.

Worked example: phishing report rate

Suppose a company sends a legitimate security-notification campaign to 80,000 recipients. It records 79,200 delivered messages after 800 hard bounces. During the next seven days, it receives 24 credible reports that recipients believed the message was phishing.

The campaign’s phishing report rate is:

phishing report rate = reported phishing messages ÷ delivered messages × 100

phishing report rate = 24 ÷ 79,200 × 100
phishing report rate = 0.0303%

The result is approximately 0.03%, or about 3 reports per 10,000 delivered messages. That is not a universal pass-or-fail threshold. The more useful question is why the reports occurred. Did recipients not recognize the sender? Did the campaign unexpectedly ask them to sign in? Did the message use a new domain, a link shortener, a new template, or language that resembled common scam patterns?

If the same sender’s previous account alerts drew 2 reports per 100,000 deliveries, a jump to 3 per 10,000 is meaningful even if the absolute number seems small. Rate changes reveal deteriorating clarity and trust earlier than raw counts alone.

How phishing attacks impersonate email senders

Phishing attempts vary in sophistication. Some are generic messages sent at high volume; others are precisely targeted attacks tailored to a company, department, vendor relationship, or executive. The delivery method and visual design may change, but most attacks rely on an identity mismatch that the recipient does not notice in time.

Display-name spoofing

A display name is the human-readable name shown beside an email address, such as “Example Billing” or “Alex Morgan.” It is easy for an attacker to choose a display name that resembles a legitimate person or department. A message could display “Example Support” while being sent from an unrelated address.

Recipients often see the display name before the full address, especially on mobile devices. Legitimate senders should therefore use a stable, recognizable From name and avoid frequent unexplained changes. Consistency makes deviations easier for recipients and security systems to notice.

Lookalike and cousin domains

Attackers may register domains that visually resemble a brand, including altered spellings, added words, swapped characters, or alternate top-level domains. A recipient might see example-security.com, examp1e.com, or example-support.co and assume it belongs to example.com.

Lookalike domains are particularly effective when an organization’s real messages already use multiple marketing, support, billing, and regional domains. Every extra sender domain can make the recipient’s mental model more complicated. A simpler domain strategy reduces ambiguity.

Spoofed From domains

A phishing email may display the victim brand’s actual domain in the From field while originating from an unauthorized system. This is one of the problems DMARC is designed to address: it lets a domain owner publish how receivers should handle mail that appears to be from the domain but does not pass aligned SPF or DKIM checks.

Spoofing should not be confused with all unauthorized use. A legitimate vendor, forwarding flow, or legacy application may also fail authentication if it was set up incorrectly. That is why senders should investigate authentication reports before moving directly to strict enforcement.

Compromised legitimate accounts

Some of the most convincing phishing messages come from real mailboxes that attackers have taken over. The message may be sent from an employee, partner, customer, or supplier address that has an established reputation and a valid history. Authentication can pass in these cases because the sender is technically authorized, even though the account is being misused.

This is why anti-phishing protection cannot stop at DNS records. Strong account security, multifactor authentication, access review, alerting for unusual sending behavior, and clear incident-response procedures matter as much as domain-level controls.

Common causes of phishing risk for legitimate senders

A legitimate company can unintentionally create conditions that resemble phishing. These choices may not make a campaign malicious, but they make it harder for recipients to verify authenticity and easier for criminals to imitate the program.

Inconsistent sender identity

Using many From addresses, domains, display names, and reply-to addresses without explaining their roles makes mail difficult to recognize. If onboarding messages come from one domain, invoices from another, support from a third, and security notices from a fourth, recipients may not know which messages are real.

Create a documented sender-identity system. Decide which domain sends transactional messages, which sends marketing mail, which address receives replies, and which display names appear for each stream. Use those choices consistently in templates, help-center content, product UI, and customer education.

Unfamiliar login or payment requests

Requests to enter a password, reset credentials, update payment details, or approve a transaction are common in phishing. A legitimate email that sends users to a raw login form without context may trigger suspicion even when it is genuine.

Whenever possible, tell recipients why they are receiving the message, what account or action it concerns, and what they can do if they are unsure. For especially sensitive actions, encourage customers to open the product directly through a saved bookmark or known application rather than relying solely on an email link.

Mismatched link domains

A visible link can say one thing while leading to another domain. That pattern is common in phishing, but it can also occur in legitimate programs that use third-party click tracking, URL shorteners, surveys, payment processors, or hosted forms.

Minimize surprises. Use branded link domains where possible, avoid generic short links for sensitive workflows, and make sure the destination domain is expected for the message type. If a customer receives a renewal notice from your company but the payment link opens an unrelated-looking host, they may reasonably hesitate.

Poorly configured authentication

An SPF record that omits an authorized provider, DKIM that is not signing properly, or a DMARC policy without alignment can make genuine messages look less trustworthy. Authentication configuration also changes over time as teams add new platforms for product email, customer support, CRM, events, invoicing, or recruiting.

Treat every new sending service as an identity change. Before it begins sending production mail, confirm its SPF and DKIM setup, evaluate whether it aligns with the visible From domain, and test the actual received message headers. Implementation details and setup guidance should be reviewed against the current email API reference and setup guides, rather than relying on copied DNS examples from an old project.

Overly urgent or generic copy

Phrases such as “act now,” “final warning,” “verify immediately,” and “your account will be closed” appear frequently in phishing campaigns. Legitimate transactional emails sometimes need urgency, but unexplained pressure undermines credibility.

Use specific context instead. Name the relevant account action, order, invoice, subscription, or security event. State what happens next and provide a support path. Do not use fear as the primary mechanism for getting a recipient to click.

Preventing phishing with SPF, DKIM, and DMARC

SPF, DKIM, and DMARC are complementary controls. They help receiving mail systems evaluate whether a message is authorized to use a domain and whether it has been altered in transit. They do not block every phishing email, but they are foundational to reducing direct spoofing of a domain.

SPF: authorize sending hosts

SPF is published as a DNS TXT record. It identifies the mail servers or services authorized to send mail for a domain. Receiving systems can compare the server that delivered the message with the sender domain’s published SPF policy.

SPF is useful, but it has limitations. It evaluates the envelope sender used in SMTP rather than necessarily the domain that a recipient sees in the visible From field. Forwarding can also complicate SPF evaluation. For those reasons, SPF should be deployed alongside DKIM and DMARC rather than used as the only control.

DKIM: sign the message

DKIM adds a digital signature to outgoing mail. The public portion of the key is published in DNS, allowing receiving systems to validate that the message was signed by an authorized domain and that signed portions of the message have not been changed.

For senders, DKIM has two important operational benefits. First, it provides a verifiable domain signal that can survive some common mail flows better than SPF. Second, it gives DMARC a path to pass when the DKIM signing domain aligns with the visible From domain.

Key management matters. Use strong keys supported by your provider, maintain the required DNS records, and rotate keys according to your security practice. Avoid removing an old key before all messages signed with it have had enough time to be delivered and validated.

DMARC: align identity, policy, and reporting

DMARC uses aligned SPF or DKIM results to evaluate whether mail using a visible From domain is authorized. It also lets the domain owner ask receiving systems to take an action when checks fail. Common policy directions are monitoring-only, quarantine, and reject.

A careful rollout is safer than jumping immediately to rejection. Start by publishing a DMARC record that requests reports and observe which systems send mail on behalf of your domain. Identify legitimate sources that fail alignment, correct their configuration, and only then consider stronger enforcement. This reduces the chance of blocking your own transactional or campaign messages.

DMARC aggregate reports can also reveal sources you do not recognize. Unknown traffic is not automatically an attack, but it is a strong prompt to investigate. Compare the sending IPs, domains, volume, and authentication results with your known systems and vendors.

Content and design practices that reduce phishing confusion

Authentication lets machines evaluate identity. Message design helps people do the same. The safest email program makes genuine mail easy to recognize and avoids training recipients to take risky actions.

Make the message recognizable

Use a stable From name, sending domain, logo treatment, typography, and footer. Include context a recipient can independently verify, such as a recent order number, the product area involved, or the account email address in a privacy-conscious form.

Do not assume a logo proves authenticity. Attackers can copy logos and layouts. Instead, combine recognizable design with predictable sender domains, clear explanations, and destinations that match the message’s purpose.

Use direct, transparent calls to action

A good call to action says what will happen after the click. “View your invoice” is more informative than “Verify now.” “Review the new team invitation” is clearer than “Action required.” The recipient should not have to guess whether the link opens a login page, a document, a payment screen, or an account setting.

Avoid attaching unexpected executable files, password-protected archives, or documents that require recipients to enable macros. If a document is genuinely necessary, explain why it is being sent and offer a safer path to retrieve it from the authenticated product.

Give recipients a no-click alternative

For high-risk actions, include a simple alternative such as “Open the app and go to Billing” or “Sign in through your usual bookmark, then visit Security Settings.” This approach reduces pressure and gives cautious recipients a safe way to act.

It also improves support outcomes. If a recipient is uncertain, they can complete the task without forwarding the message to a colleague, clicking an unknown link, or assuming the message is fraudulent.

Monitoring phishing and brand abuse

Phishing prevention is not a one-time DNS project. Domains, vendors, templates, employees, and attackers all change. Ongoing monitoring helps identify failures before they become broad recipient harm.

A practical monitoring program should include the following:

Review DMARC aggregate reports regularly. Look for unexpected sending sources, increases in failed authentication, and domains that should no longer be sending.
Monitor mail stream changes. Investigate sudden changes in complaint rate, spam placement, clicks, unsubscribe rate, or support tickets after a sender-domain or template change.
Watch for impersonation reports. Give customers and employees a clear channel to report suspicious messages claiming to be from your company.
Audit sender inventory. Maintain a current list of all platforms, applications, and teams that can send using each domain.
Search for brand impersonation. Monitor lookalike domains, fake social accounts, and fraudulent landing pages when your risk profile justifies it.
Test received messages. Inspect headers and visible content in major mailbox providers after significant sending changes.

Security and email teams should share ownership. Deliverability specialists may notice a reputation or complaint trend first, while security teams may recognize the same event as an account compromise or spoofing campaign. A shared escalation path prevents data from being siloed.

Responding when your brand is used in phishing emails

A fast, organized response limits both immediate fraud and long-term trust damage. The right response depends on whether the attack is direct spoofing, a lookalike domain, a compromised legitimate mailbox, or a fake landing page.

First actions to take

Start by preserving evidence. Save the full message, including headers, links, attachment names, delivery times, recipient reports, and screenshots. Do not rely only on a screenshot because it often omits the technical details required to identify the sending source and authentication outcome.

Then determine the attack type. Is the message actually from your domain? Does it pass SPF, DKIM, and DMARC? Is it from a confusingly similar domain? Did it originate from a known employee or vendor mailbox? The answers determine whether the next action is DNS remediation, account containment, hosting abuse reporting, customer communication, or all of the above.

Contain the source

If a legitimate mailbox or sending credential was compromised, revoke active sessions, reset credentials, investigate forwarding rules and connected applications, rotate relevant API or SMTP credentials, and review logs for other affected accounts. If an unauthorized sender is using your domain directly, validate and strengthen authentication and enforcement.

If a lookalike domain hosts a fraudulent page, collect evidence and use the registrar, hosting provider, browser safe-browsing process, and relevant abuse channels. Legal or security teams may also need to coordinate takedown requests depending on the scope and jurisdiction.

Communicate without amplifying the scam

When customers may be affected, communicate from your established channels. Explain what genuine messages from your company look like, identify the fraudulent domain or sender if appropriate, and state what customers should do if they clicked or entered information.

Avoid reproducing every malicious link in customer notices. Do not make recipients visit a suspicious email to compare details. Direct people to your official website or in-product security page through routes they already know.

Phishing prevention checklist for email senders

Use this checklist when launching a new email stream, reviewing an existing domain, or responding to recipient concerns:

Confirm that every sending domain has appropriate SPF and DKIM authentication.
Publish DMARC reporting and investigate all material unknown sources before tightening enforcement.
Keep a complete inventory of transactional, marketing, support, billing, and internal sending systems.
Use recognizable, stable From names and visible From domains.
Avoid unexpected requests for passwords, payment details, or confidential information by email.
Use transparent link destinations and avoid generic URL shorteners for sensitive actions.
Include contextual details that help recipients recognize why they received the message.
Offer a no-click route for account, billing, and security actions.
Monitor complaints, phishing reports, authentication failures, and support tickets after campaign changes.
Secure mailboxes, API keys, SMTP credentials, and vendor access with least privilege and strong authentication.
Give employees and customers a clear way to report suspicious messages.
Document an incident-response owner and escalation process before an impersonation event occurs.

The goal is not to force recipients to become email-security experts. The goal is to make legitimate communication predictable enough that unusual, deceptive messages stand out.

Conclusion

Phishing emails are malicious messages designed to exploit trust, but the defense is not limited to filtering bad mail. Legitimate senders can reduce their exposure by making their identity verifiable, their communications recognizable, and their sensitive requests safer to complete.

Use SPF, DKIM, and DMARC to protect domain identity; use consistent sender domains and clear copy to protect recipient confidence; and use monitoring plus incident response to catch abuse quickly. These measures strengthen security and support deliverability because both depend on the same outcome: recipients and mailbox providers can reliably tell legitimate email from an impersonation attempt.

FAQ

Are phishing emails the same as spam?

No. Spam is generally unwanted bulk email, while phishing is deceptive email intended to steal information, money, or access. A phishing email may also be spam, but not all spam is phishing.

Can SPF, DKIM, and DMARC stop all phishing emails?

No. They are highly important for reducing spoofing of your domain, but they cannot stop attacks from lookalike domains or compromised legitimate accounts. They should be combined with account security, monitoring, recipient education, and clear message design.

What should a legitimate email sender do if customers report phishing?

Collect the full message headers and links, identify whether the attack used spoofing, a lookalike domain, or a compromised account, contain any affected systems, and communicate through established official channels. Review DMARC data and sending logs to confirm whether your domain or infrastructure was involved.

Does a phishing report hurt deliverability?

It can. A report may indicate that recipients do not recognize or trust a message, and repeated negative recipient signals can affect future inbox placement. Investigate the message design, sender identity, link domains, timing, targeting, and authentication results rather than treating reports as an isolated support issue.

How can recipients verify whether an email is real?

They should check the full sender address and destination domain, avoid using unexpected links for sensitive actions, and sign in through a known bookmark or official app when unsure. Legitimate senders should make those safer verification paths clear in their messages.

Phishing Emails: Definition, Deliverability Risks, and Prevention