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Microsoft Defender for Office 365 vs Mimecast Email and Collaboration Threat Protection comparison

 

Comparison Buyer's Guide

Executive SummaryUpdated on Feb 11, 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 ROI with time savings, enhanced security, and operational efficiency over competitors like Mimecast.
Sentiment score
5.5
Mimecast Advanced Email Security is valued for robust protection despite challenges in quantifying ROI and gaps in support and stability.
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
 

Customer Service

Sentiment score
5.7
Microsoft Defender for Office 365 support is mixed, with prompt help for standard issues but delays in complex cases.
Sentiment score
5.6
Mimecast Advanced Email Security's technical support receives varied feedback, highlighting promptness, knowledge, but some issues with responsiveness and personalization.
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
Mimecast technical support is generally quite good.
Information Security Analyst at Enfield Central Library
I would rate my experience with technical support of Mimecast Email Security between seven and eight out of ten for their support.
Email Security Engineer at Logic Infosecurity
 

Scalability Issues

Sentiment score
7.8
Microsoft Defender for Office 365 offers seamless scalability and flexibility, adapting to organizations of all sizes without performance issues.
Sentiment score
7.0
Mimecast Advanced Email Security is highly adaptable, scalable, and rated highly for flexibility and user handling across diverse sectors.
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
If Mimecast Email Security introduces API solutions, it will dominate the market.
Email Security Engineer at Logic Infosecurity
From what I've seen from the MSP, it seems quite complicated to manage the configuration itself.
IT Manager at a logistics company with 201-500 employees
 

Stability Issues

Sentiment score
7.8
Microsoft Defender for Office 365 is stable and reliable, with minimal downtime and quick issue resolution.
Sentiment score
7.5
Mimecast Advanced Email Security is stable and reliable, with occasional login issues and rare performance interruptions reported by users.
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
 

Room For Improvement

Microsoft Defender for Office 365 requires enhanced detection, scalability, usability, support, integration, malware detection, and operating system compatibility improvements.
Mimecast Advanced Email Security is criticized for complex installation, costly pricing, and numerous functionality and support issues.
Fine-grained exceptions plus simulation mode for policies, particularly Safe Links or Attachments to test impact before enforcing it globally, are features I find missing.
IT Infrastructure & Cloud Manager at Softcell Technologies Limited
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
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
We discussed the phishing aspect, the DNS system, and the key rotation.
Senior Security Engineer at ManpowerGroup
 

Setup Cost

Microsoft Defender for Office 365 offers enterprise pricing, complex licensing, and cost-effective integration but challenges smaller organizations' budgets.
Enterprise buyers view Mimecast's email security as costly, with subscription fees per user and competitors like Microsoft Defender more affordable.
We've likely saved 30% of costs.
Designation Chief Consultant at Avtow
The standalone P2 can feel more expensive if enabled for all users, and the licensing might be somewhat confusing with terms like P1 versus P2 and feature dependency.
Technical Head Cloud Services at Softcell Technologies Limited
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
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
 

Valuable Features

Microsoft Defender for Office 365 enhances security with phishing protection, automated remediation, and threat analytics, improving organizational risk management.
Mimecast Advanced Email Security provides comprehensive protection, easy integration, user-friendly setup, and valuable insights for enhanced email security.
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
A distinct advantage of Mimecast is its ability to block phishing and impostor attacks, which are significant threats currently.
Senior Tech. Lead at WE
One of the most useful features is the threat remediation module, which can be used to remove malicious emails that may have been delivered or manually remove them.
Information Security Analyst at Enfield Central Library
Mimecast Email Security includes the best gateway solution across all Cisco, Trend Micro, and other solutions.
Email Security Engineer at Logic Infosecurity
 

Categories and Ranking

Microsoft Defender for Offi...
Ranking in Email Archiving
1st
Ranking in Secure Email Gateway (SEG)
1st
Average Rating
8.4
Reviews Sentiment
6.8
Number of Reviews
63
Ranking in other categories
Email Security (2nd), Advanced Threat Protection (ATP) (2nd), Microsoft Security Suite (8th)
Mimecast Email and Collabor...
Ranking in Email Archiving
2nd
Ranking in Secure Email Gateway (SEG)
3rd
Average Rating
8.0
Reviews Sentiment
5.9
Number of Reviews
39
Ranking in other categories
Secure Web Gateways (SWG) (15th), Office 365 Protection (2nd)
 

Mindshare comparison

As of May 2026, in the Secure Email Gateway (SEG) category, the mindshare of Microsoft Defender for Office 365 is 17.0%, down from 29.5% compared to the previous year. The mindshare of Mimecast Email and Collaboration Threat Protection is 15.9%, up from 11.3% 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 36517.0%
Mimecast Email and Collaboration Threat Protection15.9%
Other67.1%
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.
HS
Email Security Engineer at Logic Infosecurity
Experience high detection and user-friendly policies with reliable email security implementation
The system is not user-friendly because you have to create policies that are mapped in a dictionary. As an IT engineer, I understand how it works, but explaining it to another IT person can be difficult. Having more user-friendly dashboards would improve the work experience. In Mimecast Email Security, checking policies in the dictionary or gateway is very complicated, and not everyone understands this process. If you examine the Check Point portal, it's user-friendly with easily accessible tabs that anyone can explore. With Mimecast Email Security, making changes might impact existing mailboxes. The portal is complicated compared to Check Point's user-friendly interface.
report
Use our free recommendation engine to learn which Secure Email Gateway (SEG) solutions are best for your needs.
892,678 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%
Financial Services Firm
8%
Manufacturing Company
8%
Comms Service Provider
7%
Computer Software Company
11%
Financial Services Firm
9%
Comms Service Provider
6%
Government
6%
 

Company Size

By reviewers
Large Enterprise
Midsize Enterprise
Small Business
By reviewers
Company SizeCount
Small Business25
Midsize Enterprise12
Large Enterprise31
By reviewers
Company SizeCount
Small Business19
Midsize Enterprise11
Large Enterprise13
 

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, Mimecast Advanced Email Security
 

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 Email and Collaboration Threat Protection and other solutions. Updated: April 2026.
892,678 professionals have used our research since 2012.