Email security and data loss prevention (DLP) are complementary controls that protect an organisation from two different directions: email security defends against inbound threats such as phishing and malware, while DLP prevents sensitive information from leaving the organisation inappropriately, whether by accident or deliberate action. Together they address both the risk of an attacker getting in and the risk of confidential data getting out, and within Microsoft 365 are largely managed through Microsoft Defender for Office 365 and Microsoft Purview.
How Microsoft Purview supports DLP across Microsoft 365
Microsoft Purview DLP policies scan content across email, SharePoint, OneDrive and Teams for sensitive information types, such as financial data, identification numbers or content matching a custom classification defined for the business, and can automatically warn a user, block an action, or alert a compliance team depending on policy configuration. Because this applies consistently across the whole Microsoft 365 environment rather than email alone, it catches sensitive data leaving through channels beyond just outbound messages, such as a confidential file being shared externally via a SharePoint link with overly broad permissions.
Email security and DLP in practice
- A finance team member is warned by a DLP policy before sending an email containing unmasked customer payment details to an external recipient, prompting a review of whether the data should be shared at all.
- A business configures DLP policies to automatically block emails containing detected national insurance numbers from being sent outside the organisation without explicit override and justification.
- A compliance team reviews DLP policy match reports to identify which departments most frequently trigger sensitive data alerts, targeting additional training accordingly.
- An organisation extends DLP coverage to SharePoint and Teams, catching a case where a confidential document was accidentally shared with an overly broad external link.
How Advantage configures email security and DLP for clients
Advantage configures Microsoft Defender for Office 365 and Microsoft Purview DLP policies to protect against inbound email threats and prevent sensitive data leaving the organisation inappropriately, tailored to the specific types of sensitive information a business handles. We help organisations balance strong protection with a workable day-to-day experience for staff.
Frequently Asked Questions
Common questions about email security and data loss prevention in Microsoft 365.
What is the difference between email security and data loss prevention?
Email security focuses on protecting an organisation from inbound threats arriving by email, such as phishing, malware and spam. Data loss prevention focuses on the outbound side, preventing sensitive information such as customer data, financial records or confidential documents from leaving the organisation inappropriately, whether through accidental misdirection, careless sharing, or deliberate exfiltration. Both are typically managed together within Microsoft 365 since email is one of the most common channels for both types of risk.
How does DLP detect sensitive information being shared inappropriately?
Microsoft Purview DLP uses sensitive information types and trainable classifiers to recognise patterns such as credit card numbers, national insurance numbers, or content matching a defined data classification, whether in an email, attachment, SharePoint document or Teams message. Policies can then automatically block the action, warn the user with an explanation, or notify a compliance team, depending on how the policy is configured for that type of content.
What is the most common cause of accidental data loss via email?
The most common cause is simple human error, such as an email being sent to the wrong recipient through autocomplete selecting a similarly named contact, or a sensitive attachment being included in a message intended for external recipients without realising the content was confidential. DLP policies that flag or block this kind of mistake before the email is actually sent address a significant proportion of real-world data breaches, which are far more often accidental than malicious.
