A secure email gateway sits in your mail's delivery path: an MX record change routes every message through it for inspection before your server ever sees it. AegisAI connects by API instead, reviewing live mail continuously, with no MX change and no place in the delivery path to fail. Here is what that difference means in practice.
Gateways give a security team full control: every rule, every allowlist, every blocked sender is something your team configured and can audit. Many have been tuned for a long time across large install bases, which means broad categories of known-bad mail (bulk spam, established malware kits, blocklisted senders) get caught reliably and early, before a message ever reaches a mail server.
They also tend to sit at the center of a security stack, integrating with a wide range of other tooling a team already runs. For an organization that wants to own every rule and already has staff dedicated to tuning them, that control is a real advantage, not a legacy habit.
The rest of this page is about the mechanical difference between the two architectures, and what each one can and cannot see as a result. Two systems, two designs, one buying decision.
An MX change makes the gateway a mandatory stop for every message. An API connection does not.
Three consequences follow from inspecting a message a single time, at the perimeter. None of them is a defect in any product. They are properties of where the inspection sits.
A gateway scores a message against signatures, blocklists, and reputation data. A first-seen domain or a phishing message with no matching signature has nothing to be caught against. AegisAI reasons about the message instead.
A perimeter gateway only sees messages crossing the perimeter. It has no visibility into mail already inside the organization, including a compromised account sending to a coworker. That pattern is covered in vendor fraud and payment redirection.
Inspection happens once, at delivery. A link that is safe at 9am and weaponized at 2pm is not re-checked. Continuous review means a message already in a mailbox can still be pulled back, in about 3 seconds, before users see or click it.
Category-level comparison. Individual vendors differ, so check any specific claim against the product you are evaluating.
The category is moving. That deserves a straight answer rather than a footnote.
Several established gateway vendors have added an API-based product alongside their MX-based one in the last year. That is a real shift, and it is worth asking, for any specific vendor, whether the API product replaces the gateway or runs beside it as a second layer to configure.
There is no gateway mode to also maintain and no second console to reconcile it with.
This is the test that separates an architecture from an addition, and it works on any vendor, including this one.
The same difference, expressed as work your team has to schedule.
MX record change, DNS propagation, and policy configuration. Typically days to weeks before the gateway is inspecting mail in production.
Authorize API access to Microsoft 365 or Google Workspace. 5 minutes. Agents begin building behavioral context immediately.
Thirty minutes. Real attacks pulled from environments like yours (BEC, vendor fraud, credential phishing) with the reasoning behind each verdict. No setup required.
Five-minute connect · monitoring mode · disconnect any time without touching mail routing