Email and Microsoft 365
Why some emails are marked “External”
Some messages arrive with a banner or tag saying they came from outside your organization. It is easy to tune out, and worth noticing.
1 min readExplainer
The short version
That little “External” label is one of the simplest protections there is. Here is what it means and why it helps.
What it means
An “External” tag means the message came from outside your company’s email system. Mail from a customer or vendor will always have it. Mail from your colleagues should not.
Why it helps
A common scam is a message that looks like it is from a colleague, often the owner or someone in finance, but is actually sent from a lookalike or personal address. The display name is right; the tag is the giveaway.
If a message from “your CEO” is tagged External, it did not come from your CEO’s work account.
How to use it
- Notice the tag on internal-sounding requests. Payment approvals, password resets, HR documents and file shares from colleagues should not be External.
- Be extra careful with External messages that ask you to sign in or pay.
- Report it if a colleague’s name appears on an External message they did not send.
What it does not tell you
The tag only says where the message came from, not whether it is safe. A vendor whose mailbox has been taken over sends External mail that looks completely normal, and a compromised colleague’s account sends internal mail with no tag at all. It is one useful signal among several.
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