What Is an Email Security Gateway? How It Works & Benefits

SMTP-level filtering evaluates an email transaction while the sender and receiving server are communicating through SMTP. Depending on the policy, the receiving gateway can reject a message before the sender transmits the message body through DATA.

Is an email security gateway the same as a spam filter?

No. A spam filter primarily identifies unwanted messages, while an email security gateway can provide a broader security and policy layer. Gateway capabilities can include spam filtering, authentication checks, malware scanning, recipient validation, sender reputation, rate limiting, and SMTP-level rejection.

Can an email security gateway prevent phishing?

An email security gateway can reduce phishing risk by evaluating authentication, sender reputation, message characteristics, URLs, attachments, and other threat indicators. However, no single gateway can guarantee that every phishing message will be detected, particularly when attackers use compromised legitimate accounts.

Does an email security gateway replace SPF, DKIM and DMARC?

No. SPF, DKIM, and DMARC serve specific email-authentication purposes. An email security gateway can evaluate their results and use them as part of a broader security policy, but the gateway and authentication standards perform different functions.

Can an email security gateway work with Microsoft 365 or Google Workspace?

Yes. An email security gateway can be positioned in front of cloud email platforms when the platform and gateway are configured appropriately. SpamJadoo documents integrations with both Microsoft 365 and Google Workspace, including inbound gateway and connector configuration.

What does a 550 SMTP rejection mean?

A 550 response indicates that the requested SMTP action was not accepted. Under SMTP, a 550 response can be used for mailbox-unavailable conditions or policy-based rejection. An email gateway can use a 550 response to reject a message when its configured security policy determines that the transaction should not continue.

Why reject spam before the email body is accepted?