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Microsoft Defender for Office 365 vs Mimecast Advanced Email Security comparison

 

Comparison Buyer's Guide

Executive SummaryUpdated on Jun 2, 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
7.1
Microsoft Defender for Office 365 boosts efficiency, cuts phishing, integrates security, reduces tool costs, and mitigates risk.
Sentiment score
5.3
Mimecast Advanced Email Security offers substantial protection against threats, justifying its cost despite support and stability concerns.
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
There is definitely a return on investment when using Mimecast, as it blocks phishing emails, reducing the risk of significant financial losses.
Senior Tech. Lead at WE
The ROI which companies see should be able to justify buying Mimecast Advanced Email Security.
Solution Architect Cybersecurity at Microland Limited
 

Customer Service

Sentiment score
5.7
Microsoft Defender for Office 365 support is reliable but varies with subscription level and complexity of issues.
Sentiment score
5.3
Mimecast Advanced Email Security offers responsive support, though users suggest enhancements in flexibility and documentation for even better service.
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
Support personnel are hesitant to engage in remote sessions, preferring to share documentation via email.
Senior Tech. Lead at WE
The customer support for Mimecast Advanced Email Security is excellent.
Manager - EUC at Finthrive
We instantly get customer support from Mimecast Advanced Email Security whenever there is a requirement.
System Engineer II at a media company with 5,001-10,000 employees
 

Scalability Issues

Sentiment score
7.8
Microsoft Defender for Office 365 efficiently scales with cloud-native design, ensuring reliable performance and seamless integration for diverse organizations.
Sentiment score
7.0
Mimecast Advanced Email Security is highly scalable, seamlessly supporting diverse organizational sizes and large email volumes in cloud environments.
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
It handles email flow very smoothly, and we never face any issues with email delivery as our organization grows or email volume increases.
System Engineer II at a media company with 5,001-10,000 employees
If Mimecast Email Security introduces API solutions, it will dominate the market.
Email Security Engineer at Logic Infosecurity
While our user base remains around 2,200, I believe it can adapt to much larger requirements as needed, based on discussions with others managing larger organizations.
Manager - EUC at Finthrive
 

Stability Issues

Sentiment score
7.8
Microsoft Defender for Office 365 offers consistently reliable performance with minimal downtime, high user ratings, and manageable minor issues.
Sentiment score
7.5
Mimecast Advanced Email Security is highly stable, reliable, and efficient, despite occasional downtime and login issues.
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
They confirm it's a good solution where only one or two rare emails get through, while the rest are properly blocked without any issues.
Email Security Engineer at Logic Infosecurity
The issues we did have were causing quite a lot of problems.
IT Manager at a logistics company with 201-500 employees
Mimecast Advanced Email Security is a good product and is very stable.
Solution Architect Cybersecurity at Microland Limited
 

Room For Improvement

Microsoft Defender for Office 365 needs improvements in usability, false positive reduction, phishing detection, scalability, and reporting capabilities.
Mimecast Advanced Email Security needs better support, interface, accuracy, simplified admin features, competitive pricing, and enhanced phishing detection.
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
When you buy an XDR provider, they give you a complete holistic story around it, showing what has happened, which email somebody has clicked on, whether there have been any changes, and whether there is any network activity.
Solution Architect Cybersecurity at Microland Limited
A lot of emails were missed despite being known samples.
Senior Tech. Lead at WE
Mimecast Email Security is somewhat expensive compared to the competition in the Indian market.
Co-Founder & VP-Sales at QuantumShield Technologies LLP
 

Setup Cost

Microsoft Defender for Office 365 is cost-effective with E5, costly standalone, requiring careful planning for subscription-based licensing.
Mimecast Advanced Email Security is costly, with some users valuing its ROI, while others find it non-competitive.
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
The pricing is higher for Mimecast, particularly for the Indian market, where it is considered expensive.
Senior Tech. Lead at WE
Regarding the price, I think that in terms of similar products, it is pretty much in the same line, so I think it's reasonable.
IT Manager at a logistics company with 201-500 employees
Overall, my experience with pricing, setup costs, and licensing was smooth.
Manager - EUC at Finthrive
 

Valuable Features

Microsoft Defender for Office 365 enhances security with AI-driven phishing detection and robust protection across Microsoft 365 services.
Mimecast offers comprehensive email security with phishing prevention, sandboxing, and seamless Microsoft 365 integration, ensuring robust threat protection.
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
There was a signature phishing scam on the internet, but Mimecast Advanced Email Security caught it before it came to fruition and instantly blocked that signature-based phishing scam.
System Engineer II at a media company with 5,001-10,000 employees
It easily generates reports about the kinds of emails coming in weekly and classifies them into various categories, making it very helpful to analyze and ensure our email gateway remains safe and secure by updating all security patches.
Senior Managing Consultant at a tech vendor with 10,001+ employees
A distinct advantage of Mimecast is its ability to block phishing and impostor attacks, which are significant threats currently.
Senior Tech. Lead at WE
 

Categories and Ranking

Microsoft Defender for Offi...
Ranking in Email Archiving
1st
Ranking in Secure Email Gateway (SEG)
2nd
Average Rating
8.4
Reviews Sentiment
6.8
Number of Reviews
61
Ranking in other categories
Email Security (2nd), Advanced Threat Protection (ATP) (3rd), Microsoft Security Suite (8th)
Mimecast Advanced Email Sec...
Ranking in Email Archiving
2nd
Ranking in Secure Email Gateway (SEG)
3rd
Average Rating
8.0
Reviews Sentiment
5.9
Number of Reviews
44
Ranking in other categories
Secure Web Gateways (SWG) (10th), Office 365 Protection (2nd)
 

Mindshare comparison

As of July 2026, in the Secure Email Gateway (SEG) category, the mindshare of Microsoft Defender for Office 365 is 15.3%, down from 28.6% compared to the previous year. The mindshare of Mimecast Advanced Email Security is 15.2%, up from 12.0% compared to the previous year. It is calculated based on PeerSpot user engagement data.
Secure Email Gateway (SEG) Mindshare Distribution
ProductMindshare (%)
Microsoft Defender for Office 36515.3%
Mimecast Advanced Email Security15.2%
Other69.5%
Secure Email Gateway (SEG)
 

Featured Reviews

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.
Avinash Mishra - PeerSpot reviewer
Manager - EUC at Finthrive
Advanced email filtering has blocked massive spam volumes and prevents unauthorized data leaks
Improvements for Mimecast Advanced Email Security include enhancing the user interface and accessibility, particularly regarding admin capabilities to add or modify user accounts. Streamlining this could improve overall usability and security management for users. Reporting is another area needing improvement in Mimecast Advanced Email Security, as the reports provided are not very easy to decipher. With artificial intelligence being integrated into various tools including Mimecast Advanced Email Security, I believe there is potential to enhance functionality, enabling users to ask specific questions and retrieve concise answers instead of overwhelming data. I choose a nine for Mimecast Advanced Email Security because improvements such as better user interface and artificial intelligence integration features would greatly enhance its usability. While no tool is perfect, these adjustments could greatly elevate Mimecast Advanced Email Security's capabilities.
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903,807 professionals have used our research since 2012.
 

Answers from the Community

HM
Senior System Engineer at AfDB
May 4, 2023
May 4, 2023
In my opinion, all gateways including Mimecast or Defender for O365 or ProofPoint work hand-in-hand in their respective mechanics and algorithms built. And definitely has its own advantages. However, I have been using it for my customers' MDO which is far better. I would say relying on gateways is important but at the same time USER education and reporting back to the IT administrator far impor...
See 2 answers
TL
Senior IT Security Specialist at a tech services company with 1,001-5,000 employees
Apr 25, 2023
Greetings Matingou, Defender for O365 I would say would suffice as it has all the tools included in Mimecast in just one single tool, may take some time to navigate at first as it gives a lot of information in just one tool but once you know your way around, you will be able to have good visibility on your email threats landscape by provides a range of protections against email-based threats such as spam, phishing, malware, and etc. It also includes features such as URL protection and attachment scanning to prevent users from clicking on malicious links or downloading harmful files. but on the other hand, Mimecast might be needed, if you require compliance measures, including data loss prevention, archiving, and encryption. It also provides greater visibility and control over email security, allowing you to monitor and manage threats in real-time. Hope this helps.
BK
IT Manager at vTech4U
May 4, 2023
In my opinion, all gateways including Mimecast or Defender for O365 or ProofPoint work hand-in-hand in their respective mechanics and algorithms built. And definitely has its own advantages. However, I have been using it for my customers' MDO which is far better. I would say relying on gateways is important but at the same time USER education and reporting back to the IT administrator far important as well. 
 

Top Industries

By visitors reading reviews
Computer Software Company
12%
Manufacturing Company
9%
Financial Services Firm
9%
Comms Service Provider
7%
Computer Software Company
11%
Financial Services Firm
9%
Construction Company
8%
Manufacturing Company
6%
 

Company Size

By reviewers
Large Enterprise
Midsize Enterprise
Small Business
By reviewers
Company SizeCount
Small Business24
Midsize Enterprise11
Large Enterprise32
By reviewers
Company SizeCount
Small Business19
Midsize Enterprise12
Large Enterprise18
 

Questions from the Community

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.
What needs improvement with Mimecast Email Security with Targeted Threat Protection?
There is room for improvement since new threats are emerging. Considering the availability of new features would be worthwhile. Mimecast Email Security is somewhat expensive compared to the competi...
 

Also Known As

MS Defender for Office 365
Mimecast Email Security with Targeted Threat Protection, Mimecast Web Security, Mimecast Mailbox Continuity, Email and Collaboration Threat Protection
 

Overview

 

Sample Customers

Microsoft Defender for Office 365 is trusted by companies such as Ithaca College.
Azizi Developments, Affinity Credit Union, Aftercare, Al Abbar Group
Find out what your peers are saying about Microsoft Defender for Office 365 vs. Mimecast Advanced Email Security and other solutions. Updated: June 2026.
903,807 professionals have used our research since 2012.