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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
60
Ranking in other categories
Email Archiving (1st), Email Security (1st), Advanced Threat Protection (ATP) (2nd), Microsoft Security Suite (10th)
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 January 2026, in the Secure Email Gateway (SEG) category, the mindshare of Microsoft Defender for Office 365 is 24.2%, down from 31.1% 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) Market Share Distribution
ProductMarket Share (%)
Microsoft Defender for Office 36524.2%
Retarus Email Security0.8%
Other75.0%
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 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."
"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."
"The product is not resource-intensive."
"Microsoft Defender for Office 365 facilitates efficient management and updates through the cloud. We do not have to worry about incompatibilities. It just works."
"The stability of Microsoft Defender for Office 365 is fantastic."
"Microsoft Defender for Office 365's most valuable features are safe attachments and safe links."
"The features I appreciate most about Microsoft Defender for Office 365 are admin notifications for potential threats along with protecting our Microsoft apps such as Outlook from potential phishing attacks."
"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."
"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

"Too many false positives and lacks an accurate capability to detect malicious SharePoint sites."
"The inbuilt analysis of false positives can be faster. It's not slow, but it can be faster."
"This product's effectiveness could be improved, in terms of detecting unwanted spam or even malware between the emails, compared to other products."
"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."
"The visibility into threats is not up to the mark, as I do not have control. I rate my experience with Microsoft Defender for Office 365 as six out of ten due to troubleshooting and pricing concerns."
"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."
"Specifically, within Microsoft Defender for Office 365, I want it to improve the DLP capabilities."
"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

"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."
"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."
"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."
"Microsoft Defender is expensive. I typically recommend it only if clients have the budget. Otherwise, I would suggest an alternative."
"From the pricing point of view, like any other product in the market, there is scope for negotiation."
"Compared to other brands, Microsoft Defender for Office 365's pricing is competitive."
"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."
"It's a user-base subscription."
Information not available
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Top Industries

By visitors reading reviews
Computer Software Company
14%
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 Business23
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 ...
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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, Abnormal AI and others in Secure Email Gateway (SEG). Updated: January 2026.
881,082 professionals have used our research since 2012.