Gmail contact-based filtering
Gmail filter sender not in contacts: screen unknown senders automatically.
Gmail filters can match senders, words, and labels, but Gmail does not include a native sender not in contacts condition. KeepKnown adds the missing contact-based rule.
Gmail can filter exact senders and keywords, but it does not expose a native condition for everyone who is not in Google Contacts. KeepKnown uses your contacts as the allow-list and moves unknown senders into a recoverable label instead of deleting mail.
Short answer
Gmail does not have a native not-in-contacts filter.
Create Gmail filters for exact senders or words. Use KeepKnown when you need every non-contact sender moved out of the inbox.
A contact list becomes your inbox gate.
Native Gmail filters
Useful for exact senders, subjects, labels, and search operators.
Strict allow-listing
Known people pass. Outsiders move quietly to a recoverable label.
Private by design
Sender relationship decides routing, not email body text.
Questions before you connect.
Can Gmail filter senders not in my contacts?
Gmail can filter individual senders, words, and labels, but it does not offer a native rule for every sender who is not in your contacts.
Does KeepKnown delete or permanently block email?
No. KeepKnown routes outsider mail to a separate label so important messages from new senders can still be found.
Related inbox workflows
Gmail unknown senders
Move senders not in your contacts out of the inbox automatically.