How to delete or move a lot of Gmail messages
MLStrand56 had a Gmail question for the Answer Line forum: How does one archive or delete every email from a particular sender--or that matches some other criteria?
Gmail lacks an obvious, simple tool for bulk operations. There's no button to click or menu option to select for deleting or altering all of the messages or conversations that share a specific attribute. But you can still do it.
Before any bulk operations, remember that Gmail defaults to presenting your mail not in messages (what I sent to you), but in conversations (what I sent to you, your reply, my reply to your reply, and so on). So when you delete all the messages from, say, your ex, you'll also delete every other message in all of those discussions.
If that isn't what you want, turn off Conversation mode. Click the tool icon near the top-right corner and select Settings. In the General tab, select Conversation view off. You may want to turn it back on when you're done.
You start the bulk process with a search. If you want to delete all messages from a particular address, click the search field near the top of the window and type from:, followed by the address, such as from: firstname.lastname@example.org (although I hope that's not the address you want to delete.)
On the other hand, if you want to delete or move all of the messages connected to that address--from, to, cc'd, or even just referenced in the text--skip the from: label and just type in the address.
You'll soon have a list of messages that match your criteria. Click the Select button--the one with the box icon immediately to the left of the Refresh button. This will select all visible messages or discussions, but probably not all that match your search criteria. So follow that by clicking the Select all conversations that match this search link.
If you want to delete the messages, click the trash can icon. If you wish to archive them to a different location, See How to manage Gmail labels (and use them as folders).
Read the original forum discussion.