AegisAI Perspectives · 099
Cloud-native email security deploys by API, inline gateway, journaling or a hybrid, and the right one depends on whether anything may touch mail delivery.
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Cloud-native email security comes in four deployment models: an API connection, an inline gateway that needs your MX record pointed at it21, journaling, or a hybrid of gateway and API. Choose by one question: may anything sit in the path of mail delivery? AegisAI takes the API route, reading mail through the Microsoft 365 or Google Workspace API after delivery with no change to mail routing15.
Microsoft names three ways to connect a non-Microsoft service: DNS mail routing, the Microsoft Graph API, and in-and-out mail routing4. Journaling is the fourth path, and a hybrid joins a gateway to an API tool.
This page widens the gateway or AI-native choice from two options to four. List which of the four models your vendors offer before the first call.
Short on time? Watch the explainer, or book a demo.
The gateway and hybrid models do, because a gateway needs your MX record pointed at the service provider. Microsoft then tells you to lock Exchange Online down with a Partner inbound connector, so mail routed directly to Exchange Online is rejected22. With the MX record elsewhere, you enable Enhanced Filtering for Connectors instead of turning off anti-spoofing14.
Zero-hour auto purge (ZAP) does not act on high confidence phishing when the MX record points to another service and a mail flow rule bypasses spam filtering10.
Watch for in-and-out routing, where mail leaves Microsoft 365 and comes back. Microsoft says messages are then counted twice in most reporting tools, and returned messages are likely to fail email authentication checks5. For the API side in detail, read how API-based email security works without an MX record change.
Mark each model as touching delivery or not, and strike out every model that breaks your red line.
It depends on where the service sits. A gateway locked in as the only accepted route leaves inbound mail no other path while it is down. With journaling, an unavailable journaling mailbox gets journal reports retried for up to 24 hours, then a non-delivery report goes to the alternate journaling mailbox25.
On AegisAI's API design, which reads mail after delivery, mail keeps flowing while detection pauses until the service returns19.
Ask every vendor for its outage behaviour in writing, and test it in the trial window.
An admin grants mailbox permissions, and those decide what the tool can move or delete. Graph API integration typically requires full access to mailboxes. From 12/31/2026, Microsoft will block Graph API changes to sensitive fields on non-draft messages unless the app holds Mail-Advanced.ReadWrite permissions with tenant administrator consent, with an exception for specialised security uses7.
Volume has a ceiling too. The Outlook service allows 10,000 API requests in a 10-minute period and four concurrent requests for each app and mailbox pair20.
Get the permission list in writing, and mark each permission that can move or delete mail.
Work through the steps in order; each one removes options.
Write down the red line: may anything sit in the path of mail delivery?
If nothing may, rule out the gateway and the hybrid, since both need the MX record pointed at the service.
If you keep a gateway, plan the Partner inbound connector that rejects direct mail and Enhanced Filtering for Connectors.
For an API tool, list the Graph permissions it requests, starting from full mailbox access.
Check the tool against the 12/31/2026 Graph change and its Mail-Advanced.ReadWrite consent.
For journaling, pick a destination outside Exchange Online and a scope of internal, external or both.
Record each vendor's written answer on outage behaviour next to its model.
Finish the seven steps before any trial, so the trial tests one model, not four.
The table puts the four models on the same rows; the last row is where an API tool has no edge.
| Criterion | API | Inline gateway | Journaling | Hybrid | Where AegisAI sits |
|---|---|---|---|---|---|
| MX record change | None: a separate route from DNS mail routing | MX points to the service | None: a journal rule | MX points to the gateway | No change to mail routing |
| When it acts | On mail in the mailboxes, through Graph | Before Exchange Online sees the mail | On copies in journal reports | Both | After delivery |
| What the admin grants | Graph permissions, typically full mailbox access | DNS change and a Partner inbound connector | A journal rule and an outside mailbox | Both sets | Write access for removal, which the admin grants and can revoke18 |
| If the service is down | Ask the vendor | Locked-in route leaves no other path | Reports retried for up to 24 hours | Ask the vendor | Mail keeps flowing while detection pauses |
| Volume limit | 10,000 requests per 10 minutes per app and mailbox | Ask the vendor | Ask the vendor | Graph limit for the API half | Not stated on its pages |
| Holds mail before any user can see it | No | Yes | No | Yes, for the gateway half | No edge: it works after delivery |
60-second self-check
Six questions. Nothing is sent anywhere; the result shows on this page.
If holding mail before delivery is a hard rule, choose the gateway row and accept the MX change.
Illustrative example, figures are fictional. Ridgeway Builders (fictional) runs 2,500 mailboxes on Microsoft 365, and its red line is that nothing may touch mail delivery. A gateway would need the MX record pointed at the service, so it is struck out with the hybrid. Legal already journals external messages to an outside archive, which an Exchange Online mailbox cannot be; that stays as it is. The team picks an API tool. Its busiest mailbox receives 1,800 messages a day, and the vendor confirms its requests stay under 10,000 per 10 minutes for that mailbox. The admin approves 3 Graph permissions and marks the 1 that can delete mail. The tool runs read-only for 30 days before removal is switched on.
Run the same four checks on your own tenant: red line, archive, mailbox volume, permissions.
AegisAI reads mail through the Microsoft 365 or Google Workspace API after delivery. There is no change to mail routing (MX records). The platform runs in monitoring mode first17. Removal needs write access your admin grants and can revoke. If the service has an outage, mail keeps flowing while detection pauses until the service returns.
Track three numbers from the day the chosen model goes live.
To see the API model on your own mail before you commit, ask for an evaluation.
There are four: an API connection, an inline gateway, journaling and a hybrid. Microsoft lists DNS mail routing, the Graph API and in-and-out routing as the ways to connect a service. Pick the model that respects your red line on mail delivery.
No. The Graph API is a separate integration route from DNS mail routing. A gateway, and so a hybrid, needs the domain's MX record pointed at the service provider.
An inline gateway filters mail before Exchange Online sees it, through the MX record. An API tool connects through Graph, typically with full mailbox access, and works on mail in the mailboxes.
Journaling sends copies of internal messages, external messages or both to a mailbox outside Exchange Online. A tool reading those copies sees mail but does not sit on the delivery path.
Microsoft says messages are counted twice in most reporting tools, and returned messages are likely to fail email authentication checks.
Microsoft will block Graph API changes to sensitive fields on non-draft messages unless the app holds Mail-Advanced.ReadWrite with tenant administrator consent, with an exception for specialised security uses. Ask each API vendor which permission it will hold.
