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Microsoft Defender for Office 365 vs Retarus Email Security comparison

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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)
2nd
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) (3rd), Microsoft Security Suite (9th)
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 September 2026, in the Secure Email Gateway (SEG) category, the mindshare of Microsoft Defender for Office 365 is 13.9%, down from 27.5% compared to the previous year. The mindshare of Retarus Email Security is 1.2%, up from 0.4% 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 36513.9%
Retarus Email Security1.2%
Other84.9%
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 technical support is good and quick to resolve issues."
"The most valuable feature of Microsoft Defender for Office 365 is the ease of use."
"My experience deploying Microsoft Defender for Office 365 was seamless."
"The stability of Microsoft Defender for Office 365 is fantastic."
"My experience with customer support and technical support for Microsoft Defender for Office 365 has been excellent."
"The feature I like the most about Microsoft Defender for Office 365 is that it typically runs in the background—you do not know it is there until you need to access it."
"The product is not resource-intensive."
"Threat Explorer is an invaluable tool for me, and it plays a crucial role in helping me discern the origins of various email campaigns, pinpointing where they emanate from, and identifying the individuals within our organization who are affected."
"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

"This is quite an expensive solution and understanding the pricing model and features is quite complicated and it can, in fact, be a nightmare when dealing with Microsoft."
"Microsoft sometimes has downtime, and we'll get several incidents coming in back to back. We have a huge backlog of notifications, many of which may be false positives. However, there might be serious alerts, so we can't risk dismissing all of them at once."
"Several simulation options are available within 365, and the phishing simulation could be better."
"The cost of Security Copilot is up there right now, and I think it needs to come down for more people to adopt."
"Microsoft Defender for Office 365 should be more proactive."
"The certification training for Defender for 365 needs to be deeper and incorporate Sentinel. I took all the security courses except one, and Sentinel isn't included."
"The pre-sales cost calculations could be more transparent."
"I assess the stability and reliability of the solution as seven out of ten."
"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

"The product is expensive."
"The pricing has become expensive."
"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."
"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."
"I was working in the government and it was too expensive for us to use our Microsoft products."
"Microsoft Defender for Office 365 comes with Microsoft Windows. It is free with the operating system."
"It is much more expensive than using another solution because we have had to include some options and upgrade our license."
"Defender for 365 comes in various plans and licenses, along with other Microsoft security solutions. Purchasing this kind of package or security bundle gives good value for money, and that's what I recommend."
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Top Industries

By visitors reading reviews
Computer Software Company
11%
Manufacturing Company
9%
Financial Services Firm
8%
Comms Service Provider
8%
No data available
 

Company Size

By reviewers
Large Enterprise
Midsize Enterprise
Small Business
By reviewers
Company SizeCount
Small Business24
Midsize Enterprise11
Large Enterprise32
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 Proofpoint, Microsoft, Mimecast and others in Secure Email Gateway (SEG). Updated: September 2026.
914,394 professionals have used our research since 2012.