Email Security

The Top 10 Alternatives To Microsoft Defender For O365

The top alternatives to using Microsoft Defender For Office 365, based on security features, reporting and ease of use.

The Top 10 Alternatives To Microsoft Defender For Office 365 Include:
  • 1. Abnormal Security
  • 2. Barracuda Email Protection
  • 3. Darktrace For Email
  • 4. Inky
  • 6. Mimecast
  • 7. Proofpoint Essentials
  • 8. SpamTitan
  • 9. Tessian
  • 10. Trustifi

Microsoft Defender for Office 365 is an email security solution developed by Microsoft, designed to provide enhanced protection against spam, phishing, business email compromise, and malware. Defender for O365 is available to all O365 users and is offered in three tiers.

The first, Exchange Online Protection, provides basic protection against broad, high volume email attacks, such as spam. This is free to all O365 users. The second, Microsoft Defender for 0365 P1, provides greater protection against advanced and zero-day malware, phishing attacks, and business email compromise. This is available as part of Microsoft 365’s E5 subscription tier. 

Finally, Microsoft Defender for Office 365 P2 is an advanced option, adding more threat investigation and reporting options, with automated response and phishing simulation for training users to avoid scams. This is available as an add-on service.

Microsoft Defender for O365 is a popular email security service for O365 users. It can be cost-effective, it’s easy to configure, and it has some strong security features, which work across Microsoft services including Teams, SharePoint, and OneDrive.

However, there are some drawbacks. Licensing can be confusing; some security features are not as well developed as other security solutions on the market, and some organizations will have additional compliance requirements that Defender for O365 does not meet. 

To help organizations decide which email security service is the right fit, we’ve put together a guide to the best alternative email security solutions to Defender for Office 365. We’ll consider what users like and dislike, key security features, and ease of use when assessing each vendor on this list.

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Abnormal Security Logo

What Users Like: High accuracy of the solution, with low false positive rate; quick deployment and integration.

Abnormal was founded in 2018, and is headquartered in San Francisco, CA. Their product, Abnormal Security, is a cloud email security platform that sits inside your email inbox to catch email threats designed to bypass traditional email security gateway services, such as phishing and business email compromise. These emails are tricky to catch as they may not contain any malicious content, but instead aim to trick users.

Abnormal catches these advanced threats by analyzing thousands of email signals, including message content, time stamps, and sender data. These signals are compared to a baseline of normal email behavior to detect ‘abnormal’ email content. Our testing has found this system to be highly accurate.

Abnormal integrates with Microsoft 365 in minutes, with no changes required to MX-records required. It works similarly to Defender for O365 in that it adds an extra layer of email defense, using API connections to enhance Microsoft’s inbuilt security technologies. It also provides in-depth reporting on attacks found, with an intuitive and well-designed admin console.

We’d recommend Abnormal as a strong alternative to Microsoft 365, particularly for organizations looking for enhanced protection against phishing and business email compromise attacks.

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Barracuda Logo

What users like: Barracuda Sentinel is very effective at catching phishing emails; the email gateway stops spam and malware.

Barracuda is a well-established email security provider, headquartered in Campbell, CA. Email Protection is their enterprise email security stack, providing automated inbound email defense, inbox protection, automated threat remediation, user awareness training and email compliance with email archiving, backup, and recovery.

Barracuda’s email protection is unique on this list, as it includes both a secure email gateway (SEG) solution, and internal email protection utilizing API-based integration with Microsoft 365. Barracuda’s SEG is a market leading service, based on threat data from over 200,000 companies worldwide. It provides strong filtering against inbound threats such as malware, ransomware, and malicious web links.

Barracuda’s internal email service, Barracuda Sentinel, sits inside the email inbox and protects against more sophisticated email scams, such as spear-phishing and account takeover attempts using an artificial intelligence engine.

Barracuda Email Protection is available in three plans: Advanced, Premium, and Premium Plus. We would recommend Barracuda to organizations looking for comprehensive email protection, combined with backup and archiving features.

Darktrace Logo

What Users Like: Automated threat response and alerts users to suspicious email content.

Darktrace is a UK-based security provider, known for their AI-powered solutions for network security. Darktrace for Email uses artificial intelligence to learn your email networks and prevent suspicious content email content from reaching your users. It’s designed to prevent sophisticated email attacks such as advanced phishing, account takeover, and domain spoofing.

Darktrace’s AI engines are designed to learn the typical behaviors of your email users. It can then spot deviations from these baselines, and automatically remediation suspected incidents. The platform is fully cloud-based and can be installed in Microsoft 365 in a few minutes via API-connections.

Darktrace adds a strong level of security to the inbuilt controls offered by Microsoft 365, and — unlike many other providers on this list — its threat protection platform extends to Microsoft Teams, SharePoint, and OneDrive. It also provides comprehensive reporting and automated protection when attacks are detected.

We recommend Darktrace to enterprises looking for cloud-based email protection for Microsoft 365 that extends across all of Microsoft’s application suite.

Inky logo

What Users Like: Easy to understand email warnings for end users; intuitive admin console.

Inky is a cloud-based email security platform designed to add an extra-layer of protection against phishing and malware for Microsoft 365. Inky uses machine learning systems to learn your users’ email behaviors, helping it to detect email threats more accurately. Inky was founded in 2008 and is headquartered in College Park, Maryland.

When malicious emails are detected, Inky shows a customizable warning banner to the end user. A gray banner is used to signify an email is external, but not suspicious. A yellow banner is used to signify that an email is suspicious and that users should be cautious. A red banner is used to warn that an email is likely to be malicious. If preferred, admins can configure these messages to be sent to an email quarantine. These banners also extend to outbound email messages: when Inky detects a user has attached a sensitive attachment, it will warn the user not to send or to confirm the recipient prior to sending.

One of Inky’s main differentiators against other vendors in this list are its mobile email security capabilities. Inky’s warning banners work across all email clients on any device, so protection extends to users even when they are using their smartphone to reply to work email. In addition, it provides comprehensive reporting and threat insights for admins.

We recommend Inky to organizations looking for highly user-friendly email protection, particularly to prevent attacks that target your users, such as phishing and account compromise.


What Users Like: Powerful email protection against phishing.

IRONSCALES is an inbox-layer email security solution, integrating with Office 365 via API connection and providing enhanced protection against internal email threats, including phishing, social engineering, and account takeover attacks. IRONSCALES was founded in 2013 and is headquartered in Atlanta, Georgia.

IRONSCALES provides powerful protection against email threats inside the email inbox. It provides highly effective malware and attachment protection, with real-time scanning even after email delivery based on multiple anti-virus engines. A recent update has extended this protection across Microsoft 365 application, including Microsoft Teams and SharePoint. It uses machine learning algorithms to detect indications of suspicious email messages, and then displays warning banners to users on suspicious emails.

In addition, IRONSCALES allows users to report suspicious emails directly to admins, with granular threat remediation policies that allow admins to decide if the emails are automatically quarantined or marked as suspicious. When a user reports an email, this is processed across the entire IRONSCALES network, meaning high-volume phishing attacks are quickly identified and blocked.

Alongside email security, IRONSCALES also provides comprehensive reporting, security awareness training, and phishing simulation to test users’ ability to spot suspicious email messages.

We’d recommend IRONSCALES as a highly effective alternative to Defender for O365 when it comes to phishing detection and automated remediation.

Mimecast Logo

What Users Like: Powerful attachment sandboxing and message scanning; granular policy management.

Mimecast is a market leading email security provider with a powerful secure email gateway designed to protect enterprise email networks. Mimecast’s SEG provides inbound and outbound email filtering, URL and attachment protection, domain impersonation protection, browser isolation technologies to secure against harmful web content and internal email protection with automated removal of harmful emails inside the email inbox.

Mimecast are known for their powerful email filtering service, based targeted inspection of all inbound, outbound, and internal email messages. Admins can configure granular email policies to augment these email filters to ensure harmful emails cannot reach users. Mimecast’s email filtering includes a 100% anti-virus and 99.5% anti-spam SLA.

Mimecast includes a cloud-based admin console, which enables simplified deployment into Office 365 with integrations with Azure Active Directory. The platform includes detailed reporting and enables user access to spam reports, helping to free up admin time.

We’d recommend Mimecast for enterprise organizations looking for a powerful email gateway as an alternative to Microsoft Defender for O365.

Proofpoint Logo

What Users Like: Powerful email protection; useful reporting for admins; user-friendly email quarantine.

Proofpoint Essentials is a leading email security platform, designed with small-and-midsized organizations in mind. Proofpoint collect and analyze more than 100 billion data points a day from more than 100 million email boxes and secure more than 50% of the Fortune 100, the top 5 banks globally and 7 of the top 10 global retailers.

Proofpoint Essentials includes a secure email gateway, with protection against advanced threats including phishing and malware. It also includes encryption, email archiving, email continuity, and data loss protection for a multi-layered email security stack. Our testing has found PPT’s threat protection to be very effective.

Proofpoint integrates easily with Office 365, leveraging Azure Active Directory for simplified deployment. It provides admins with granular email controls, starting at a basic level for smaller teams, up to more granular options where organizations need it. Proofpoint also provides end-user access to their own spam reporting, allowing them to archive, release or delete spam messages where required.

We’d recommend Proofpoint Essentials to small and midsized organizations looking for comprehensive email protection with strong admin controls and effective email filtering.

SpamTitan Logo

What Users Like: Cost-effectiveness; ease of implementation, support, and flexibility.

TitanHQ is a business security provider headquartered in Galway, Ireland. They provide solutions designed for small and midsized organizations, including a secure email gateway, DNS Filtering, email archiving, security awareness training, and email encryption. Their solutions are known for ease of use and cost-effectiveness.

SpamTitan is TitanHQ’s secure email gateway platform, providing protection against inbound and outbound email threats, including spam, viruses, malware, and malicious weblinks. SpamTitan has a powerful anti-spam solution with a 99.9% catch rate, making it a strong alternative to Microsoft Defender for O365 when it comes to spam filtering. SpamTitan also allows users to access their own email quarantine, so that if genuine emails are marked as spam they can be easily accessed.

One of SpamTitan’s key differentiators against competitors is ease of use. The platform deploys easily with O365 and is straightforward to configure, with admin user-friendly interface and policy configuration. It’s also one of the most affordable solutions on this list, with monthly billing and simplified licensing.

We would recommend SpamTitan for organizations looking to improve spam and malware filtering in Office 365, especially those looking to combine this with a cost-effective security stack that includes web security, encryption, archiving and security awareness training.


What Users Like: Strong user experience; helpful warning banners on email messages; easy configuration.

Tessian, founded in 2013 with headquarters in San Francisco and London, is an email security solution designed to prevent human error in email – ‘oh s*it moments’ as they describe. This includes phishing emails, sending emails to the wrong recipient, or sending the wrong attachment in an email, potentially causing data loss, financial harm, or compliance fines in regulated industries such as healthcare and compliance.

Tessian is deployed via API to cloud based email platforms and uses machine learning systems to understand the historical context of your email communications, creating ‘relationship graphs’ around who users normally interact with over email. The platform then uses real-time analysis of email content to detect suspicious content and suspected mistakes, displaying a warning banner to users and alerting them before an error is made.

Tessian’s feature set is broadly split into three areas: phishing prevention, data loss prevention and threat intelligence. Phishing prevention includes real-time scanning for malicious content, including indicators of account compromise, or ransomware. Data loss prevention includes measures to prevent data being sent to the wrong recipients accidentally, by warning users before they hit send.  Threat intelligence is designed to give you data on each attack, with user-level reporting.

Tessian is a strong alternative to Defender for O365, particularly for organizations in highly regulated industries looking to reduce human error, alongside improving email security.

Trustifi Logo

What Users Like: Highly effective, user-friendly email encryption and ‘One-Click Compliance.’

Trustifi is a cloud-based email security and email encryption provider which enables organizations to secure against email threats and protect against data loss in email messages. Trustifi Inbound Shield scans email content in real-time to detect and remediate against malicious links, harmful attachments, and phishing attacks. Trustifi provides secure email encryption to outbound messages, automatically encrypting emails containing sensitive data with a ‘One-Click Compliance’ feature.

Trustifi is one of the best encryption providers in the market when it comes to ease of use for the end user. Admins can configure encryption to take place automatically, with machine learning engines used to detect and automatically secure sensitive content to protect against data loss and ensure legal compliance.

Recipients can access encrypted email directly from their email inbox, with a two-step verification process used to authenticate access. Email senders have far greater control over encrypted email, with the ability to edit sent email, unsend email messages, or revoke access to attachments.

Trustifi’s inbound threat protection secures against email threats including phishing, spoofing and impersonation attempts, business email compromise, and spam – all managed from a central admin dashboard with customizable policy configuration.

Trustifi is easy to deploy with Office 365 and is a good alternative to Defender for Office 365 for organizations looking for user-friendly email encryption for compliance and inbound email security.

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The Top 10 Alternatives To Microsoft Defender For O365