AegisAI Perspectives · 109
Stop misdirected email with recipient warnings, a short send delay and a DLP rule on attachments in Microsoft 365 and Gmail, since recall rarely works.
See it on your own Google Workspace or Microsoft 365 tenant. No MX change.
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Turn on recipient warnings, give every message a short send delay, and add a DLP rule for attachments. In Gmail, Undo Send holds a message for up to 30 seconds17. AegisAI checks who an email is going to and whether that is normal for the sender before delivery2.
Recall works only inside one Microsoft 365 organization, so this page sets up the other controls in order, in Microsoft 365 and Gmail. Buying a product for this is a separate question, covered in the guide to choosing outbound email DLP for Microsoft 365.
Work through the three in that order, because each one catches what the one before it missed.
A misdirected email is a message, often with a file, sent to someone who should not have it. In the Verizon 2025 report, misdelivery was the top action in Miscellaneous Errors breaches, at 72% of action varieties involving end-users22.
The compliance cost is a reporting clock. The EU GDPR counts the unauthorised disclosure of personal data as a personal data breach23. Where feasible, the controller notifies the supervisory authority within 72 hours of becoming aware of it, unless the breach is unlikely to put people at risk. Name the person who decides on notification before the first wrong email goes out.
Short on time? Watch the explainer, or book a demo.
Warnings work because they appear while the message is still being written. MailTips are messages Outlook shows during composing, so a user hears about a problem before sending7. The External Recipients MailTip is off by default, and an admin turns it on with the Set-OrganizationConfig cmdlet. The Large Audience MailTip fires when a group has more than 25 members by default.
Gmail starts from the other side. External recipient warnings are on by default, and changing them needs the Gmail Settings administrator privilege18. Check both settings in your tenants this week.
You can stop it during a delay, and rarely after. In classic Outlook, a rule can delay delivery of all messages by up to two hours12. After Send, each message waits in the Outbox for the time you set. Under Gmail Undo Send, a user picks a cancellation period of 5, 10, 20 or 30 seconds.
Recall is narrower. It works only when sender and recipient both have Microsoft 365 work or school accounts in the same organization, and the recipient has not opened the message14. Personal accounts such as Gmail, Hotmail or Outlook.com cannot use recall. Set the delay, and write recall out of your incident plan as a control.
A DLP rule reads the file, which a warning about the recipient does not. Microsoft policy tips work when sensitive information is in the body, the subject line or an attachment11. In Outlook on the web and Outlook 2013 and later, the tip shows above the recipients while the message is written.
A Gmail DLP rule can block outgoing messages, quarantine them for an administrator, or let the user proceed after a warning20. With several attachments, the rule triggers if any one of them matches. Start with a warn action on files that hold personal or financial data.
Warnings read the domain and DLP rules read the file, and the wrong person can pass both. Gmail does not show its external warning for contacts and directory members19, so a saved client or the wrong colleague gets no prompt. Autocomplete feeds the error, and in Outlook on the web the whole Auto-Complete List cannot be deleted, only one entry at a time16.
Pattern rules add a second gap. The outbound DLP page on aegisai.com puts it plainly: regex rules fire on routine payroll and miss the leak to a personal inbox, so teams tune them down25. Remove stale contractor and client entries from autocomplete, and test one rule on a payroll file sent to a new address.
An agent-based check runs after the user presses Send and before the email is delivered. On the outbound DLP page cited here, the check covers what is in the email, who it is going to and whether that is normal for the sender, then applies your policy. It sits behind the warnings and delays above and works alongside them. Keep the composing-time warnings on even after you add such a check.
Set the controls up in this order, one platform at a time.
In Microsoft 365, turn on the External Recipients MailTip with Set-OrganizationConfig, since it is off by default.
Confirm the Large Audience MailTip threshold, which is more than 25 members by default.
In the Google Admin console, confirm external recipient warnings are still on.
Add a classic Outlook rule that delays all outgoing mail, up to two hours.
Ask Gmail users to set Undo Send to 30 seconds.
Create a Microsoft Purview DLP policy with policy tips that cover attachments.
Create a Gmail DLP rule with the warn action for outgoing files.
Remove recall from the incident plan as a control, and note its limits.
Tick each step off and record the date it went live in each tenant.
Each method stops a different mistake, so the gaps between them show where a wrong file still gets out.
| Control | What it stops | Microsoft 365 | Gmail | AegisAI |
|---|---|---|---|---|
| External recipient warning | Wrong outside address | Off by default, admin turns it on | On by default | Checks who the email is going to |
| Send delay or undo | Instant regret | Rule delays up to two hours | Undo window up to 30 seconds | Not covered on the product page |
| Recall | Sent message | Same organization, unopened only | Not available for Gmail addresses | Not covered on the product page |
| Attachment rule | Sensitive file | Policy tips cover attachments | Warn, quarantine or block | Applies your policy before delivery |
| Normal for the sender | Unusual recipient for this sender | Not covered in the Microsoft pages used here | Not covered in the Google pages used here | Whether that is normal for the sender1 |
| Block before delivery in Gmail | Wrong file in Gmail | Not applicable | Block action on outgoing mail | No edge: not available on Google Workspace |
Score your own tenant on each row, and use the demo request page to test one policy on your live outbound mail.
AegisAI reads who sends sensitive data and to whom, checks whether that is normal, then applies your policy. A policy runs in audit on live outbound mail, then is raised to alert. Actions depend on the platform, and pre-delivery blocking is not available on Google Workspace. Outbound email DLP is in early access, which runs on the connection you already have.
Illustrative example, figures are fictional. At 16:02 an HR assistant types "Jor" and autocomplete picks a former contractor instead of the payroll provider. The attachment holds 140 staff bank details. The External Recipients MailTip is still off, so no warning shows. A two minute Outbox delay rule holds the message, and a DLP policy tip appears above the recipients. The assistant reads the tip, sees the wrong name and deletes the message at 16:03. Without the delay, recall would have failed, because the contractor is outside the organization.
Walk your own HR and finance teams through this timeline and find the step your tenant is missing.
Track three numbers from the day the controls go live.
Review all three on day 30 and add a block action where warnings were sent anyway.
Turn on external recipient warnings, add a send delay or undo window, and put a DLP rule on attachments. In Exchange Online the external MailTip is off until an admin turns it on. Do not count on recall.
Not in Outlook on the web. You cannot delete the entire Auto-Complete List there, so unwanted entries are deleted one at a time. Remove old contractor and client addresses first.
The longest Undo Send period is 30 seconds, from a choice of 5, 10, 20 or 30 seconds. Set it to 30 for staff who send files outside.
Only after an admin turns it on. The External Recipients MailTip is off by default and is turned on with Set-OrganizationConfig. Gmail shows its external warning by default.
No. Personal accounts such as Gmail, Hotmail or Outlook.com cannot use Outlook message recall. Recall works only inside one Microsoft 365 organization, before the message is opened.
