Open Gmail
Click the search bar at the top
Type `in:all` or search for the sender, subject, or keyword
Press Enter
Look for emails that are not in the Inbox but still appear in search results
Open the email
To find archived mail by label, click More in the left sidebar and select All Mail
Scroll or search within All Mail to locate archived emails
On mobile, open the Gmail app
Tap the search bar
Enter a sender, subject, or keyword
Search in All Mail if needed
Open the archived email from the results