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Microsoft Defender for Office 365 vs Retarus Email Security comparison

 

Comparison Buyer's Guide

Executive Summary

Review summaries and opinions

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

Categories and Ranking

Microsoft Defender for Offi...
Ranking in Secure Email Gateway (SEG)
1st
Average Rating
8.4
Reviews Sentiment
6.8
Number of Reviews
61
Ranking in other categories
Email Archiving (1st), Email Security (2nd), Advanced Threat Protection (ATP) (2nd), Microsoft Security Suite (9th)
Retarus Email Security
Ranking in Secure Email Gateway (SEG)
15th
Average Rating
8.0
Reviews Sentiment
5.6
Number of Reviews
1
Ranking in other categories
No ranking in other categories
 

Mindshare comparison

As of March 2026, in the Secure Email Gateway (SEG) category, the mindshare of Microsoft Defender for Office 365 is 19.9%, down from 30.0% compared to the previous year. The mindshare of Retarus Email Security is 0.8%, up from 0.2% 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 36519.9%
Retarus Email Security0.8%
Other79.3%
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.
WAKKAS AHMAD - PeerSpot reviewer
Security Consultant at Mahle
Provides valuable reports that make it easy to take action
Our primary use case for this solution is protecting emails This solution has helped our organization by protecting our emails from various threats. It helped us get customized reports on all of the emails we received on the user side and other data. The feature I found most valuable was getting…

Quotes from Members

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

Pros

"Microsoft Defender for Office 365 is a stable solution."
"Technical support is very good. They are knowledgeable and respond quickly."
"Microsoft Defender for Office 365 saves me time; it does save a lot of time, especially with the automation."
"One of the best features of the tool is its capability to aggregate insights from different workloads, basically from the Office 365 and endpoints part."
"Defender enables us to secure all 365-related activity from a single place. It gives us visibility into everything happening in Outlook, protecting us against phishing and other email-based threats. Defender helps us detect any suspicious behaviors."
"The most valuable feature of Microsoft Defender for Office 365 is its spam filter."
"Microsoft Defender for Office 365's most valuable features are safe attachments and safe links."
"The most valuable feature is the integration; it's a single console, so we don't have to switch around between multiple products, and another valuable feature is the ease of operations and maintenance."
"The feature I found most valuable was getting details on the emails, being alerted once those emails got a bad reputation, and then being able to take action on those emails."
 

Cons

"In some situations, it has not been able to pick impersonated emails having no attachments. Technical support definitely has a scope for improvement."
"Microsoft Defender for Office 365 could improve by giving customers information on techniques to prevent threats."
"They can improve their security in a way where a customer can know if all their attachments are safe or not to open through a report. The solution does its job perfectly, but it never reports to the customer whether those attachments have been stopped before or not."
"You should be able to deploy Defender for every subscription without the need to add servers."
"The visibility for the weaknesses in the system and unauthorized access can be improved."
"Microsoft Defender for Office 365's Mac functionality requires improvement to deliver the same level of protection found on Windows devices."
"The only thing they should improve is the licensing model. They should stop changing it. A year ago, the five features I mentioned were included in one product. Now, three of them are bundled into one product, and you have to pay extra for the other two. I don't mind paying extra, but I don't want them to change it every year or every six months. I need to know what I'm looking at and not worry about it next year."
"From a development point of view, if I wanted to do development on my actual machine where Defender is, the organization can set certain policies or Defender makes that prohibitive."
"This solution needs to improve the area of GUI as well as dashboards because they are very poor in terms of the current email security solution."
 

Pricing and Cost Advice

"It's a user-base subscription."
"The solution could be better by simplifying the business model of their licensing. It was hard to figure out how to get the licensing done for the environment, initially."
"Compared to other brands, Microsoft Defender for Office 365's pricing is competitive."
"The product is very expensive."
"The product is expensive."
"Microsoft Defender for Office 365 is an add-on to the Office license. Many customers are purchasing this solution."
"The license is expensive because the cost is based on the number of users."
"For licensing, it's usually a yearly package for customers who are subscribed to Office 365, but they can also pay on a monthly basis."
Information not available
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Top Industries

By visitors reading reviews
Computer Software Company
13%
Financial Services Firm
8%
Manufacturing Company
8%
Comms Service Provider
6%
No data available
 

Company Size

By reviewers
Large Enterprise
Midsize Enterprise
Small Business
By reviewers
Company SizeCount
Small Business24
Midsize Enterprise10
Large Enterprise31
No data available
 

Questions from the Community

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.
What is your primary use case for Microsoft Defender for Office 365?
My use case for Microsoft Defender for Office 365 is for email protection, safe links, protection of links, documents, protecting my documents, and protecting attachments. I also use it to conduct ...
Ask a question
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Also Known As

MS Defender for Office 365
No data available
 

Overview

 

Sample Customers

Microsoft Defender for Office 365 is trusted by companies such as Ithaca College.
Information Not Available
Find out what your peers are saying about Microsoft, Proofpoint, Mimecast and others in Secure Email Gateway (SEG). Updated: February 2026.
884,976 professionals have used our research since 2012.