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Fortinet FortiMail vs Microsoft Defender for Office 365 comparison

 

Comparison Buyer's Guide

Executive SummaryUpdated on Nov 2, 2025

Review summaries and opinions

We asked business professionals to review the solutions they use. Here are some excerpts of what they said:
 

ROI

Sentiment score
6.7
Fortinet FortiMail boosts email security, reduces costs, and saves time, enhancing operational efficiency through seamless integration and advanced features.
Sentiment score
6.9
Microsoft Defender for Office 365 offers strong ROI through security enhancements, cost savings, and improved company productivity despite measurement challenges.
It offers cost savings compared to Cisco, which was very expensive.
System admin at Environment Fund
It has also decreased our time to detection and response by about 15 to 20 percent.
Technology support manager at Alfred State College
Overall, cost of owning and operating our system goes down.
Designation Chief Consultant at Avtow
It's hard to quantify the return on investment we've seen from Microsoft Defender for Office 365.
Chief Architect at a tech vendor with 1,001-5,000 employees
 

Customer Service

Sentiment score
6.4
Fortinet FortiMail's customer service is generally praised for efficiency, especially elite support, despite occasional standard support delays.
Sentiment score
5.8
Microsoft Defender for Office 365 users rate support highly, praising its responsiveness and 24/7 availability, despite occasional documentation and communication issues.
I have direct communication with Kenyan system engineers and local support in Ethiopia, enabling good support.
Network & Security Engineer at Malam Engineering PLC
Mainly, they are focusing on Fortinet FortiMail and FortiAnalyzer, where the support engineers are very good.
Head of the IT Security Division at a tech services company with 11-50 employees
Fortinet's technical support offers high-quality support.
System admin at Environment Fund
Over the past two years, there have been no critical problems.
Solution Consultant at BIM Group of Companies
we opened tickets, and they typically resolve them quickly.
Chief Architect at a tech vendor with 1,001-5,000 employees
With a subscription for Microsoft Defender for Office 365, it is an eight. Without it, it is a six.
Manager at a tech services company with 10,001+ employees
 

Scalability Issues

Sentiment score
7.2
Fortinet FortiMail is scalable and flexible, efficiently adapting to varying organizational sizes, though some hardware limitations exist.
Sentiment score
7.8
Microsoft Defender for Office 365 offers scalable, efficient protection for large enterprises, ensuring seamless growth across diverse industries.
The scalability of Fortinet FortiMail depends on whether you are buying a virtualized license, which allows for a scalable pay-as-you-go model, or if you are buying a box.
Head of the IT Security Division at a tech services company with 11-50 employees
Fortinet FortiMail is scalable and can be expanded in large environments.
Senior Associate at a tech vendor with 10,001+ employees
We have never faced scalability problems, and Microsoft manages it effectively.
Solution Consultant at BIM Group of Companies
Microsoft Defender for Office 365 scales transparently for us, as we grew from 1,000 users to 3,000 users, and we didn't notice much difference.
Chief Architect at a tech vendor with 1,001-5,000 employees
Microsoft Defender for Office 365 scales with the growing needs of my company well.
Senior Client Director and Advisory Service Leader at Crossfuze
 

Stability Issues

Sentiment score
8.3
Fortinet FortiMail is highly stable and reliable, with rare issues quickly resolved and seamless integration with other Fortinet tools.
Sentiment score
7.7
Microsoft Defender for Office 365 provides 99.9% uptime with minor issues, ensuring reliable performance and seamless cloud integration.
This stability is consistent across Fortinet products, including FortiGate firewall.
Network & Security Engineer at Malam Engineering PLC
I would rate the stability of Microsoft Defender for Office 365 as 10 over 10 because it's highly available, it works, and it does the job it is meant to do.
Cloud Solutions Architect at a tech services company with 201-500 employees
I have not experienced any downtime, crashes, or performance issues because of Defender.
Technology Associate at a financial services firm with 51-200 employees
The solution is stable, as we have been using it for the past two years.
Solution Consultant at BIM Group of Companies
 

Room For Improvement

Fortinet FortiMail needs a more intuitive interface, better integration, enhanced security, simpler encryption, and improved spam filtering.
Users call for enhanced virus detection, cross-platform support, and pricing transparency in Microsoft Defender for Office 365.
Providing comprehensive documentation on how to deploy and configure would improve the solution.
Network & Security Engineer at Malam Engineering PLC
The transition from on-premises devices to virtual appliances may be necessary as more organizations migrate email services to the cloud.
Head of computer systems at Indian Institute of Space Science & Technology(IIST)
There are also false positives issues, especially with signed PDF attachments.
Senior Associate at a tech vendor with 10,001+ employees
The main area for improvement is simplifying the implementation and rollout process.
Infrastructure and Security Lead at Vedanta
Microsoft could improve by offering recommendations for domain spoofing attacks, especially scenarios where DNS records like SPF, DKIM, and DMARC are not properly published.
Solution Consultant at BIM Group of Companies
There is a different console for different things; I just want one consolidated console.
Senior Director, Security Architecture & Engineering at a leisure / travel company with 10,001+ employees
 

Setup Cost

Fortinet FortiMail offers competitive, scalable pricing with flexible licensing, valued for performance and security despite some expense concerns.
Microsoft Defender for Office 365 pricing is seen as flexible but potentially expensive, offering value in comprehensive security features.
Fortinet FortiMail is considered overpriced by Indian rupee standards.
Head of computer systems at Indian Institute of Space Science & Technology(IIST)
The setup cost is a little bit costly.
Senior Associate at a tech vendor with 10,001+ employees
We've likely saved 30% of costs.
Designation Chief Consultant at Avtow
Money-wise, it is a part of the Office 365 suite, making it slightly more expensive compared to Trend Micro.
Infrastructure and Security Lead at Vedanta
Microsoft is quite affordable with a lot of features available for any size organization.
Solution Consultant at BIM Group of Companies
 

Valuable Features

Fortinet FortiMail excels in email security with user-friendly features, advanced threat protection, and seamless integration with Fortinet products.
Microsoft Defender for Office 365 enhances email security with anti-phishing, anti-malware, threat intelligence, and seamless integration for efficient management.
Its threat detection capabilities have been beneficial.
System admin at Environment Fund
The most valuable features are Fortinet FortiMail's ability to protect from advanced features of email-based attacks, including protection against ransomware and malware attacks.
Network & Security Engineer at Malam Engineering PLC
Fortinet FortiMail offers capabilities like settings for mail delivery, mail filtering, spam controls, and email bursting prevention.
Head of computer systems at Indian Institute of Space Science & Technology(IIST)
It ranks the threats and allows us to prioritize those hitting us the hardest, such as email threats.
Technology support manager at Alfred State College
It provides end-to-end visibility on email threats such as phishing, extending beyond Exchange Online Protection.
Solution Consultant at BIM Group of Companies
The value of the DLP feature is significant to us because we have internal data, sometimes sensitive, and the users may not always be aware of security and privacy, which might lead them to send out information mistakenly to external parties.
Chief Architect at a tech vendor with 1,001-5,000 employees
 

Categories and Ranking

Fortinet FortiMail
Ranking in Email Security
6th
Average Rating
8.6
Reviews Sentiment
6.9
Number of Reviews
67
Ranking in other categories
No ranking in other categories
Microsoft Defender for Offi...
Ranking in Email Security
1st
Average Rating
8.4
Reviews Sentiment
6.8
Number of Reviews
60
Ranking in other categories
Email Archiving (1st), Advanced Threat Protection (ATP) (2nd), Microsoft Security Suite (10th), Secure Email Gateway (SEG) (1st)
 

Mindshare comparison

As of January 2026, in the Email Security category, the mindshare of Fortinet FortiMail is 3.5%, down from 5.5% compared to the previous year. The mindshare of Microsoft Defender for Office 365 is 9.6%, down from 13.9% compared to the previous year. It is calculated based on PeerSpot user engagement data.
Email Security Market Share Distribution
ProductMarket Share (%)
Microsoft Defender for Office 3659.6%
Fortinet FortiMail3.5%
Other86.9%
Email Security
 

Featured Reviews

Abhimanyu Das - PeerSpot reviewer
Senior Associate at a tech vendor with 10,001+ employees
Targeted email filtering has reduced spam and phishing and now saves significant investigation time
The best features of Fortinet FortiMail include its techniques and tactics, which are highly effective compared to other solutions such as Microsoft 365. Although Fortinet FortiMail may not be as advanced in some aspects, it is well recognized for its strong performance in handling spam and phishing. It performs thorough mail scanning and also offers a sandboxing feature that enhances protection. Fortinet FortiMail has had a positive impact on my organization by significantly reducing unwanted email activities such as spam and phishing. It provides accurate detection and generates results that often exceed what can be achieved through manual analysis. Since deploying Fortinet FortiMail, I have observed a reduction in investigation time by at least 20 to 30 percent.
Emeka Ndulu - PeerSpot reviewer
Cloud Solutions Architect at a tech services company with 201-500 employees
Improves threat visibility and response while reducing manual tasks and training users against phishing
I appreciate the attack simulation feature whereby I get to train users and educate them on how to identify phishing emails and spam emails, as well as the anti-spam protection. It gives me visibility into my threat environment and threat landscape to ensure that I am one step ahead of any likelihood of threats within my environment. I get to detect it and respond, so the threat intelligence is very effective. Microsoft security solutions save my time. It saves money because once I protect my environment, I don't lose money. It has decreased my detection time and my time to respond.
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Top Industries

By visitors reading reviews
Computer Software Company
13%
Financial Services Firm
10%
Manufacturing Company
7%
Government
6%
Computer Software Company
15%
Financial Services Firm
8%
Manufacturing Company
8%
Comms Service Provider
6%
 

Company Size

By reviewers
Large Enterprise
Midsize Enterprise
Small Business
By reviewers
Company SizeCount
Small Business32
Midsize Enterprise22
Large Enterprise15
By reviewers
Company SizeCount
Small Business23
Midsize Enterprise10
Large Enterprise31
 

Questions from the Community

What is your experience regarding pricing and costs for Fortinet FortiMail?
Fortinet FortiMail is considered overpriced by Indian rupee standards. My organization is not profit-making, and academic pricing is required, but it may not be available for security products like...
What needs improvement with Fortinet FortiMail?
In my opinion, points for improvement for Fortinet FortiMail include sometimes the speed and fine-tuning the false positive problems, especially with the signed PDF attachments and the whitelist an...
What do you like most about Microsoft Defender for Office 365?
Threat Explorer is an invaluable tool for me, and it plays a crucial role in helping me discern the origins of various email campaigns, pinpointing where they emanate from, and identifying the indi...
What needs improvement with Microsoft Defender for Office 365?
The inbuilt analysis of false positives can be faster. It's not slow, but it can be faster.
 

Also Known As

FortiMail
MS Defender for Office 365
 

Overview

 

Sample Customers

Magromer Cueros y Pieles S.A.
Microsoft Defender for Office 365 is trusted by companies such as Ithaca College.
Find out what your peers are saying about Fortinet FortiMail vs. Microsoft Defender for Office 365 and other solutions. Updated: December 2025.
879,422 professionals have used our research since 2012.