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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 (8th)
Retarus Email Security
Ranking in Secure Email Gateway (SEG)
16th
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 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 Retarus Email Security is 1.0%, 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 36517.0%
Retarus Email Security1.0%
Other82.0%
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

"The email protection is excellent, especially in terms of anti-phishing policies."
"I would say that 90% of the spam and phishing attack emails get blocked right off the bat."
"The insights provided with Microsoft Defender for Office 365 are helpful because it comes with the E5 license, and by default, we can use a lot of capabilities."
"Microsoft Defender for Office 365 is a stable solution."
"Scalability-wise, I do not think there are any issues so far."
"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."
"The most valuable feature of Microsoft Defender for Office 365 is its spam filter."
"The deployment capability is a great feature."
"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

"Microsoft could improve by offering recommendations for domain spoofing attacks, especially scenarios where DNS records like SPF, DKIM, and DMARC are not properly published."
"Microsoft wants its well-paying customers to finish testing some of its half-baked products, find bugs, and report bugs back to Microsoft's team, which is a little frustrating for those who have to manage it and roll it up to thousands of people across the organization."
"About eight months ago, we started to measure the quantity of phishing and spam that we have been receiving, and it has been increasing a lot. That means that protection for our email is not as good as we were expecting."
"In some situations, it has not been able to pick impersonated emails having no attachments. Technical support definitely has a scope for improvement."
"Several simulation options are available within 365, and the phishing simulation could be better."
"The inbuilt analysis of false positives can be faster. It's not slow, but it can be faster."
"I am generally satisfied with how it currently is. If I could improve anything, I would reduce the cost."
"Configuration requires going to a lot of places rather than just accessing one tab."
"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

"While Microsoft Defender for Office 365 necessitates pricier E3 or E5 subscriptions, the extensive functionality offered by these licenses across various Microsoft products justifies the investment."
"Compared to other brands, Microsoft Defender for Office 365's pricing is competitive."
"From the pricing point of view, like any other product in the market, there is scope for negotiation."
"Microsoft Defender for Office 365 comes with Microsoft Windows. It is free with the operating system."
"The product is very expensive."
"For large enterprise organizations, they can definitely afford it, but for small and medium organizations, they might struggle to cover the expenses."
"The pricing has become expensive."
"The product is expensive."
Information not available
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Top Industries

By visitors reading reviews
Computer Software Company
12%
Financial Services Firm
9%
Manufacturing Company
8%
Comms Service Provider
7%
No data available
 

Company Size

By reviewers
Large Enterprise
Midsize Enterprise
Small Business
By reviewers
Company SizeCount
Small Business24
Midsize Enterprise12
Large Enterprise31
No data available
 

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.
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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: May 2026.
893,244 professionals have used our research since 2012.