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Fortinet FortiMail vs Microsoft Defender for Office 365 comparison

 

Comparison Buyer's Guide

Executive SummaryUpdated on Feb 8, 2026

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
6.4
Fortinet FortiMail enhances email security with cost savings, reduced spam, efficient management, robust features, and improved productivity.
Sentiment score
7.1
Microsoft Defender for Office 365 boosts efficiency, cuts phishing, integrates security, reduces tool costs, and mitigates risk.
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
6.5
Fortinet FortiMail support is praised for responsiveness and expertise but criticized for variability based on region and tier.
Sentiment score
5.7
Microsoft Defender for Office 365 support is reliable but varies with subscription level and complexity of issues.
I have direct communication with Kenyan system engineers and local support in Ethiopia, enabling good support.
CTO 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
7.1
Fortinet FortiMail is scalable for various environments, suitable for mid-sized to enterprise users with virtual and on-premise options.
Sentiment score
7.8
Microsoft Defender for Office 365 efficiently scales with cloud-native design, ensuring reliable performance and seamless integration for diverse organizations.
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 Cybersecurity Engineer at Kyndryl
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 rated for stability, reliability, effective spam handling, and seamless integration, requiring minimal fine-tuning.
Sentiment score
7.8
Microsoft Defender for Office 365 offers consistently reliable performance with minimal downtime, high user ratings, and manageable minor issues.
This stability is consistent across Fortinet products, including FortiGate firewall.
CTO 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 requires interface refinement, improved features, better documentation, and enhanced integration with advanced threat detection and Fortinet’s ecosystem.
Microsoft Defender for Office 365 needs improvements in usability, false positive reduction, phishing detection, scalability, and reporting capabilities.
Providing comprehensive documentation on how to deploy and configure would improve the solution.
CTO 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 Cybersecurity Engineer at Kyndryl
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 appliance-based pricing, with flexibility and reliability, though higher than open-source alternatives.
Microsoft Defender for Office 365 is cost-effective with E5, costly standalone, requiring careful planning for subscription-based licensing.
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 Cybersecurity Engineer at Kyndryl
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 provides strong security, usability, scalability, and performance for email threat detection and content control in diverse environments.
Microsoft Defender for Office 365 enhances security with AI-driven phishing detection and robust protection across Microsoft 365 services.
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.
CTO 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
5th
Average Rating
8.6
Reviews Sentiment
6.8
Number of Reviews
68
Ranking in other categories
No ranking in other categories
Microsoft Defender for Offi...
Ranking in Email Security
2nd
Average Rating
8.4
Reviews Sentiment
6.8
Number of Reviews
61
Ranking in other categories
Email Archiving (1st), Advanced Threat Protection (ATP) (3rd), Microsoft Security Suite (9th), Secure Email Gateway (SEG) (2nd)
 

Mindshare comparison

As of August 2026, in the Email Security category, the mindshare of Fortinet FortiMail is 2.7%, down from 4.0% compared to the previous year. The mindshare of Microsoft Defender for Office 365 is 5.7%, down from 11.6% compared to the previous year. It is calculated based on PeerSpot user engagement data.
Email Security Mindshare Distribution
ProductMindshare (%)
Microsoft Defender for Office 3655.7%
Fortinet FortiMail2.7%
Other91.6%
Email Security
 

Featured Reviews

Abhimanyu Das - PeerSpot reviewer
Senior Cybersecurity Engineer at Kyndryl
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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910,454 professionals have used our research since 2012.
 

Top Industries

By visitors reading reviews
Construction Company
9%
Financial Services Firm
8%
Manufacturing Company
8%
Computer Software Company
8%
Computer Software Company
11%
Manufacturing Company
9%
Financial Services Firm
9%
Comms Service Provider
7%
 

Company Size

By reviewers
Large Enterprise
Midsize Enterprise
Small Business
By reviewers
Company SizeCount
Small Business32
Midsize Enterprise23
Large Enterprise15
By reviewers
Company SizeCount
Small Business24
Midsize Enterprise11
Large Enterprise32
 

Questions from the Community

What needs improvement with Fortinet FortiMail?
I think they should improve Fortinet FortiMail on-premises by enhancing its user interface. Additional features they could have in the future would include advanced analytics capabilities. I do thi...
What is your primary use case for Fortinet FortiMail?
I do have a partnership with Fortinet. I have been both a partner and reseller.
What is your experience regarding pricing and costs for Microsoft Defender for Office 365?
My experience with pricing, setup, and licensing is that it's actually quite reasonable even on the licensing side as a standalone product. It's very competitive compared to what competitors are ch...
What needs improvement with Microsoft Defender for Office 365?
I think Microsoft Defender for Office 365 can be improved by creating more educational pieces about not just looking for malware. We are seeing a lot more malware-less emails that Defender for Offi...
What is your primary use case for Microsoft Defender for Office 365?
My main use cases for Microsoft Defender for Office 365 include email hygiene.
 

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: August 2026.
910,454 professionals have used our research since 2012.