Create a rule to filter blank senders

Two questions I get asked too often is "How can I filter blank senders?" and "But Outlook doesn't support a NOT rule, like Outlook Express does."

Ok, so that last one isn't really a question, but it does have an answer that begins with Yes: "Yes, Outlook supports a NOT rule." Outlook uses Exceptions to provide NOT filtering and while it seems backwards to apply a rule 'to everything, expect this thing' instead of using NOT in the initial condition, it does work.

In Outlook 2003 and newer, create a rule that applies to all messages except with @ in the sender's address:

If you use Exchange server, you need to add "/ou" to the rule for mail from coworkers. The rule will read: with '@' or '/ou' in the sender's address. This is because mail from other Exchange users (inside your network) don't have an @ in their address.

Open Rules & Alerts.
Click New Rule.
Select Apply Rule on Messages I receive, click Next.
Click Next again (rule will apply to all messages).
Choose the desired Action: move to a folder or delete the message. Click Next.
Choose except with specific words in the sender's address.
Click on specific words and type @ in the field.
Complete the rule and return to Outlook.

Outlook 2002 and older

In older versions, you are limited to using the From field or look for words in the message header.

A 'words in the message header' rule works in all versions of Outlook that support "words in the header" conditions but you can't differentiate between the From and To fields, so it only works for spam filtering if both fields are blank, if you set additional conditions, or use other rules to move or process your valid mail first.

See Create rules that apply to an entire domain for the steps needed to use @ (or an incomplete address) in the From field when creating a rule.

Using the From field condition, the rule looks at the display name not the underlying email address.

A From rule works on the actual display name:

This rule only works if both the To and From fields are blank or if you use other rules before this one (containing a stop processing condition) or add conditions to fine tune it:

Using the From field works only in corporate modes of Outlook 98/2000, not Internet Mail mode. You can also use it with Outlook 2002 and newer.

Published May 13, 2011. Last updated on October 25, 2020.