How to prevent spam email from reaching Junk folder while not blocking legitimate email

Disable this rule: “Apply to all messages” + “Permanent delete” with an @ exception is not a safe way to identify senderless spam and could permanently delete legitimate messages.

The absence of a visible address does not prove that a message has no sender; the address may be concealed or displayed differently from the underlying message header. Conversely, spam can contain a syntactically valid address with @, so the exception is neither reliable nor protective.^1^

Replace it with a reversible rule

1. Open File → Manage Rules & Alerts.
2. Clear the checkbox beside no sender address to disable it. Do not select Run Rules Now while its action is permanent deletion.
3. Open several examples of this spam and inspect their Internet headers/message details.
4. Look for a distinctive value shared only by the spam, such as repeated text in From, Return-Path, or another header. Do not use @, an empty-looking display name, or another generic value.
5. Create a rule through File → Manage Rules & Alerts → New Rule → Apply rule on messages I receive.
6. Select with specific words in the message header and enter the distinctive repeated text.
7. Initially choose move it to the specified folder, creating a folder such as Suspected spam. Outlook supports creating, editing, disabling, and manually running rules from Rules and Alerts.^2^
8. Review that folder for several days. If there are no false matches, change the action to delete it. Permanent deletion should be used only after the condition has proved reliable.

Also note that Outlook evaluates junk mail before processing rules, so an Inbox rule cannot reliably prevent messages already classified as spam from reaching the Junk Email folder.^3^

Protect legitimate senders

Add important individual addresses—not a generic @ entry—to Safe Senders:

Home → Block/Junk → Junk E-mail Options → Safe Senders → Add

Addresses on that list are not treated as junk. You can also enable Also trust email from my Contacts and Automatically add people I e-mail to the Safe Senders List if appropriate.^4^

Safe Senders protects against junk classification, but it should not be treated as an exception to a separate catch-all deletion rule. If retaining any broad rule, add explicit exceptions for trusted addresses or domains and test it using a move action first.

Continue reviewing Junk periodically and mark legitimate messages Home → Report → Not Junk. Outlook’s Junk Email Filter is designed to move suspected spam rather than prevent delivery, and Microsoft recommends checking that folder for false positives.^5^

References

1. Email without the @ sign - Microsoft Q&A
2. [Classic Outlook](https://support.microsoft.com/outlook/mail/manage-email-messages-by-using-rules-in-outlook)
3. Use Clutter to sort low-priority messages in Outlook on the web | Microsoft Support
4. [Classic Outlook](https://support.microsoft.com/outlook/mail/block-or-unblock-senders-in-outlook)
5. Overview of the Junk Email Filter in classic Outlook | Microsoft Support