Email is no longer just a place where messages arrive. For most companies, it has become the control center of digital work. Password resets, login confirmations, invoices, contracts, CRM notifications, cloud services and government messages often go through corporate email.

In practice, a corporate mailbox is often more important than it seems. If an attacker gains access to one email account, they do not only read messages. They may try to reset passwords for other services, intercept documents, change payment details in invoices, or start a new attack on behalf of an employee.

That is why email security should not rely on a strong password alone. A password can be stolen, entered on a phishing website, reused after an old data breach, or exposed through malware. Multi-factor authentication, or MFA, adds another layer of verification and significantly reduces the risk of unauthorized access.

In this article, we will look at what MFA for email means, which authentication methods are commonly used, why SMS codes are no longer a reliable long-term option, and how companies can gradually move toward stronger protection for corporate email.

Why email is one of the main targets for attackers

Many attacks against companies do not begin with complex server vulnerabilities or advanced technical exploits. Quite often, the first step is much simpler: an employee receives an email, follows a link and enters a password on a page that looks almost identical to the real login form.

Email is useful for attackers because it helps them move further. Access to a mailbox can reveal which services the company uses, who it works with, what documents are exchanged, who approves payments and which internal processes can be manipulated.

After gaining access to corporate email, an attacker may be able to:

• reset passwords for other services;
• access corporate documents;
• intercept communication with clients or partners;
• change payment details in invoices;
• send phishing emails on behalf of the company;
• collect additional information for attacks against executives or accounting teams.

Sometimes one rushed morning is enough. An employee opens a message about a supposedly full mailbox, follows a link, enters a password — and within minutes, new messages may be sent from their account to colleagues, clients or suppliers.

You can read more about such scenarios in our article on protection against social engineering.

Why a password alone is no longer enough

A strong password is still necessary. But today it does not solve the problem on its own. Even a very strong password can be compromised not by brute force, but through user behavior or an external data breach.

In real life, the same situation appears again and again: a company requires complex passwords, forces employees to change them regularly, but leaves corporate email without a second factor. As a result, one successful phishing email can make the entire password policy almost meaningless.

A password may become known to an attacker if:

• a user enters it on a fake login page;
• the same password is reused on another service;
• an external service suffers a data breach;
• malware is active on the user’s device;
• the user is tricked into revealing the password during a scam call.

In these cases, password length, special characters and regular password changes are no longer enough. The password is simply known to the attacker. This is where multi-factor authentication becomes essential.

What MFA for email means

MFA (Multi-Factor Authentication) is an authentication method where a password alone is not enough to sign in. The user must confirm their identity with at least one additional independent factor.

In simple terms, even if a password is stolen, the attacker still cannot complete the login without additional verification.

Factor type	Example
Something the user knows	Password or PIN code
Something the user has	Smartphone, hardware token, FIDO2 security key
Something the user is	Fingerprint or face recognition

For email accounts, the most common approach is a combination of a password and a second factor: an authenticator app code, push confirmation or a hardware security key.

It is important to understand that MFA does not make a company invulnerable. It does not replace employee training, backups or access control. But it is one of the most effective ways to stop many attacks that begin with stolen credentials.

Which MFA methods are used to protect email

Not all multi-factor authentication methods provide the same level of protection. One option may be convenient for a quick start, while another may be better suited for administrators, finance teams or employees with access to confidential information.

Verification method	Security level	Advantages	Limitations
SMS code	Basic	Easy to deploy	SIM-swapping, interception and phishing risks
Authenticator app (TOTP)	High	Does not depend on a mobile operator	The code can still be phished
Push confirmation	High	Convenient for users	Possible MFA fatigue attacks
FIDO2 Security Key	Very high	Phishing-resistant authentication	Requires a physical key

For a small company, an authenticator app is already a major improvement. For critical accounts, FIDO2 should be considered from the start.

Why SMS codes should not be considered reliable MFA anymore

SMS codes were once a convenient and familiar way to add a second factor. They are still better than having no MFA at all. But it is difficult to call them reliable protection for corporate email today.

The problem is that a phone number is not always fully under the user’s control. It can be targeted through SIM-swapping, messages can be intercepted on a compromised device, or the code can simply be tricked out of the user during a phishing attack.

• SMS messages can be intercepted or redirected;
• a phone number can be attacked through SIM-swapping;
• a user may enter the code on a fake website;
• the phone may be lost or compromised.

SMS should therefore be treated as a temporary or minimum level of protection, not as a target solution for corporate email security.

We covered this topic in more detail in the article Why SMS codes no longer provide an adequate level of protection.

Authenticator or FIDO2: what is better for corporate email?

Authenticator apps are a good practical solution for most companies. They do not depend on SMS, work even without mobile network coverage and significantly improve security compared to password-only login.

Common options include:

• Microsoft Authenticator;
• Google Authenticator;
• 2FAS Authenticator;
• Aegis;
• other TOTP applications.

But there is an important nuance. If a user lands on a well-made phishing page, they may enter not only the password but also the one-time code. In some attacks, this may be enough for the attacker to use the code quickly and complete the login.

FIDO2 works differently. A hardware key does not simply confirm that the user has the device. It also verifies the domain where authentication is taking place. If the website is fake, the key will not confirm the login.

This is why FIDO2 is called phishing-resistant authentication. For ordinary users it may look like a small technical detail, but for corporate email security it makes a fundamental difference.

How MFA works in Microsoft 365

Microsoft 365 supports several multi-factor authentication methods. A company can start with Microsoft Authenticator and gradually move critical or administrative accounts to FIDO2 hardware keys.

Commonly used methods include:

• Microsoft Authenticator;
• push confirmation;
• one-time codes;
• FIDO2 hardware security keys;
• Windows Hello for Business.

In a corporate environment, MFA should not be configured manually for each user if it can be avoided. It is better to manage authentication through Microsoft Entra ID security policies. This allows the company to consider the user’s role, login location, device type and risky activity.

For example, administrators may be required to use a FIDO2 key, while regular employees use an authenticator app. This is a reasonable balance between security and usability.

How to enable MFA in Google Workspace and Gmail

Google also provides strong support for multi-factor authentication. For a personal Gmail account, it is enough to enable two-step verification in the account security settings. For business use, it is better to manage this centrally through Google Workspace.

An administrator can:

• require MFA for all users;
• set a mandatory transition period;
• allow or require security keys;
• monitor suspicious sign-ins;
• limit access according to company policies.

Google has supported FIDO2 and hardware security keys for many years, so companies already using Google Workspace do not need to build a complex separate infrastructure to move toward stronger authentication.

Do other corporate email systems support MFA?

Yes, but it depends on the specific platform and configuration. Microsoft 365 and Google Workspace include MFA as part of their ecosystems. With self-hosted or less common email solutions, additional modules or integration with external authentication systems may be required.

MFA can be implemented for:

• Zimbra Collaboration;
• Roundcube;
• Kerio Connect;
• IceWarp;
• mail servers using LDAP or Active Directory;
• hybrid corporate environments.

It is also important to check legacy mail protocols and clients. Sometimes a company enables MFA for web login but leaves older connection methods that bypass modern protection. It is like locking the front door while leaving a service entrance open.

Common mistakes when implementing MFA for email

Enabling MFA is only the first step. What matters more is implementing it in a way that actually works and does not create a false sense of security.

Common mistakes include:

• Protecting only some accounts. If only part of the team uses MFA, attackers will look for the weakest account.
• Forgetting administrator accounts. Administrative accounts should be protected first.
• Leaving SMS as the main method. It is better than nothing, but weaker than authenticator apps or FIDO2.
• Not preparing recovery access. A lost phone or security key should not block the company’s work.
• Not explaining the changes to employees. People should understand why MFA is needed and how to use it.
• Not reviewing sign-in logs. Suspicious login attempts are often visible before an incident becomes serious.

There is another common problem: MFA is treated as a one-time project. It is enabled, checked off and forgotten. But security does not work that way. Policies need to be reviewed, unused accounts removed, unnecessary access revoked and infrastructure changes reflected in authentication rules.

Why FIDO2 is the strongest option for corporate email

The main advantage of FIDO2 is not simply that the user has a physical key. Its real value is phishing resistance.

A one-time code can be seen and entered on a fake website. A push request can be approved accidentally if the user is repeatedly annoyed by prompts. A FIDO2 key, however, will not confirm login on the wrong domain.

This is especially important for corporate email because many attacks begin with an attempt to make the user visit a fake login page.

FIDO2 is especially useful for:

• Microsoft 365 or Google Workspace administrators;
• company executives;
• accounting and finance teams;
• legal teams and employees working with contracts;
• employees processing personal data;
• technical specialists with access to critical services.

Not every company needs to start with FIDO2 for all employees. But for critical accounts, it is no longer excessive. It is becoming a normal part of modern cybersecurity practice.

How to implement MFA for email in a company

Moving to MFA does not have to be painful. The worst option is to force a second factor on everyone overnight and expect people to figure it out themselves. A gradual approach works much better.

1. Audit email accounts. Identify which services are used, who has administrative rights, which accounts are critical and whether there are old accounts that should have been disabled long ago.
   
2. Protect administrators first. Administrative accounts should have the strongest protection. FIDO2 or another phishing-resistant method is recommended for them.
   
3. Connect key employees. Accounting, executives, legal teams and employees with access to confidential documents should receive MFA immediately after administrators.
   
4. Prepare short instructions. Not all employees are equally comfortable with authenticator apps or security keys. A short instruction with a few screenshots often removes most questions.
   
5. Plan recovery access. There should be a clear procedure for lost phones, broken devices or employee absence.
   
6. Monitor sign-in logs. Periodic review of suspicious sign-ins helps detect problems before they turn into incidents.
   

This step-by-step approach helps improve security without creating chaos inside the company.

Need help implementing MFA?

Smart Lab helps companies implement multi-factor authentication for Microsoft 365, Google Workspace, GitLab and other corporate services. We help assess the current level of protection, choose the right MFA method, configure access policies and move toward phishing-resistant authentication based on FIDO2.

Get a consultation

Conclusion

Corporate email is not just a communication channel. In many companies, it acts as the main key to other services. Password resets, login confirmations, financial communication and business correspondence all pass through it.

If email is protected only by a password, the risk remains too high. MFA does not solve every cybersecurity problem, but it makes most typical attacks much harder. For critical accounts, FIDO2 should be considered because it provides phishing-resistant authentication.

For small businesses, this is no less important than for large companies. Often it is even more important: small businesses usually have fewer resources for incident investigation, legal consequences and recovery after a breach. It is better to protect email before it becomes the weak point of the entire infrastructure.

Frequently Asked Questions

What is MFA for email?

MFA for email is multi-factor authentication where access to an email account requires not only a password, but also an additional verification method such as an authenticator app code, push confirmation or a hardware security key.

Is a strong password enough to protect email?

No. A strong password is important, but it can still be stolen through phishing, a data breach or malware. That is why corporate email should use MFA.

What MFA method is best for corporate email?

For most companies, an authenticator app is a good starting point. For administrators, executives, accounting teams and other critical accounts, FIDO2 hardware keys are a stronger option.

Should SMS codes be used for MFA?

SMS codes are better than no MFA, but they are no longer considered an optimal protection method. For corporate email, authenticator apps or FIDO2 are preferable.

Do Microsoft 365 and Google Workspace support MFA?

Yes. Microsoft 365 and Google Workspace support multi-factor authentication, including authenticator apps, push confirmation and FIDO2 hardware security keys.

Can MFA be implemented for a self-hosted mail server?

In most cases, yes. It depends on the specific email system, but many solutions support MFA directly or through integration with LDAP, Active Directory or external authentication services.

Read also

• 2FA in GitLab: how to enable two-factor authentication
• Why SMS codes no longer provide an adequate level of protection
• Protection against social engineering: how to recognize modern attacks